CA1228000A - Chromium appearance passivate solution and process - Google Patents

Abstract

Abstract An aqueous acidic solution and process for treating metal surfaces, particularly zinc and zinc alloy surfaces, to impart improved corrosion resistance thereto. The solution contains effective amounts of A) hydrogen ions to provide a pH of about 1.5 to about 2.2, B) an oxidizing agent, C) at least one of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures or cerium ions or mixtures thereof, or instead of C) iron and cobalt ions. Other treating solutions also incorporate D) chromium ions substantially all of which are in the trivalent state, and iron ions in combination with an additional metal from C) or cerium ions, or A), B), C) and D) and F), a bath soluble and compatible silicate compound or A), B), C) and D) and G), a mixture of 1-hydroxvethylidene-1,1 diphosphonic acid and citric acid or mixtures of A), B), C) and D) with two or more of E), F) and G). The treating solution may optionally further contain halide ions and a wetting agent.

Description

l. 1228000 CHROMIUM APPEARANCE PASS IVATE SOLUTION
AND PROCESS

The present invention relates to ~assivation of metal surfaces to impart the apPearance of a chromium passivate.
A variety of chromium containing aqueous 5. solutions have heretofore been used or proposed for treating zinc, zinc alloy, cadmium, cadmium alloy and aluminium surfaces for improving the corrosion resistance properties thereof and to further enhance the appearance of such surfaces by imparting a yellow or a blue-bright 10. coating thereto, the latter simulatiny a chromium finish. Su~h treating solutions originally contained chromium in the hexavalent state and in more recent years the chromium constituent was present as a mixture of the hexavalent and trivalent forms. The reduced 15. toxicity of trivalent chromium and the increased simplicity and efficiency in treating waste effluents containing trivalent chromium has occasioned an i~lcreased commercial use of passivate solutio~s in which the chromium constituent is substantially entirely in the 20. trival~nt state. Such prior trivalent chromium passiv-ating solutions have been found to be somewhat less effective than the traditional hexavalent chromium passivating solutions in imparting good corrosion resistance to zinc and zinc alloy, cadmium, cadmium 25. alloy, and aluminium, aluminium alloy, magneslum and magnesium alloys surfaces and there has, accordingly, been a contlnuing need for further improvement in trivalent chromium passivating solutions and processes.
The excellent corrosion protection provided by 30. hexavalent chromium passivating solutions is generally associated with a light yellow iridescent passlvate ,~ , t-film which has been recognised and embodied in ASTM
specifications. Conventionally, trivalent chromium passivate films are of a clear to light-blue colour and are of inferior corrosion protection than the 5. yellow hexavalent passivate film. This problem has been further aggravated by a conversion from convent-ional cyanide zinc and cadmium plating ~rocesses to acid and alkaline non-cyanide eIectroplating baths which ~roduce metal deposits which are not as -10. receptive to chromium passivate treatments.
Ty~ical of ~rior art com~ositions and ~rocessesfor treating metal surfaces are those disclosed in United States Patents Numbers 2,393,663; 2,559,878;
3,090,710; 3,553,034; 3,755,018; 3,795,549; 3,880,772, 15. 3,932,198; 4,126r490; 4,171,231; British Patent Numbers 586,517 and 1,461,244; and German Patent No 2,526,832.

122~00~

According to its broadest as~ect the ~resent invention provides an aqueous acidic solution useful in the treatment of receptive metal substrates to imPart a passivate film thereon comprising 5. A~ hydrogen ions to provide an acidic pH;
B) an oxidizing agent: and ~) at least one or iron, cobalt, nickel,molybdenu~, manganese, aluminium, lanthanum, lanthanide mixture or cerium ions or mixtures thereof in an amount effective 10. to impart increased corrosion resistance to the treated substrate.
The present invention is particularly applicable but not limited to the treatment of alkaline and acidic non-cyanide zinc and cadmium electrodeposits to impart 15. improved corrosion resistance thereto. Particul~rlv satisfactory results are obtained on decorative zinc and cadmium electrodeposits of the bright and semi-bright types although beneficial effec~s are also achteved on zinc and zinc alloy substrates such as galvanized 20. substrates, zinc die castings and substrates comnrised of cadmium or alloys of cadmium predominantly com~rised of cadmium. While the invention in its various asnects as herein described is particularly dlrected to the treatment of zLnc and zinc alloy surfaces, it has been 25. observed that beneficial results are also obtained in the treatment of aluminium, aluminium alloy, maqnesium and magnesium alloy surfaces to orm a passivate ellm or coating thereon. ~ccordingly, the present inventlon ln lts broad sense is directed to the treatment of metal 30. surfaces which are receptive to the formatlon of a passivate film thereon when contacted wlth the solution ~22800~) of the present invention in accordance with the process parameters disclosed.
In accordance with the process aspects of the present invention, zinc, cadmium, zinc alloy, cadmium 5. alloy, aluminium and magnesium surfaces are contacted with the aqueous acidic treating solution, at a tem~er-ature ranging from about 40 up to about 150~ ( 4 to 66C) for a period of time typically ranging from about 10 seconds up to about 1 minute to form the 10. desired passivate film.
A treating bath formulation in-accordance with the various aspects of the present invention which are described in detail below may be applied to a substrate to be treated by spray, immersion, flooding or thellike 15. for a period of time sufficient to form the desired passivate film thereon. The treating solution is controlled within a temperature range of about ~0 to about 150F ( 4 to 66C), with a temperature range of about 70 to about 90F ( 21to 32C) being ~ref~rred.
20. Temperatures above about 90F ( 32C) have a tendency to cause a rapid loss of the peroxide-type oxidizing agents when used whereas temperatures below about 70F
( 21 C) reduce the activity of the bath requiring lncreased contact times to achieve a passivate fllm of 25. the same ~hickness or colour intensity as can be achieved at the hlgher temperatures at short time intervals.
Typically, contact times of about 20 or 30 seconds to about 1 minute are satlsfactorily with contact times of about 30 seconds b~ing usually preferred.
30. According to a first aspect of the present invention 12~8~)0~

there is provided a passivating solution which does not contain any chromium ions and is effective for imparting corrosion resistance to zinc, cadmium and aluminium surfaces as well as alloys thereof.
5. This aspect of the present invention provides a treating solution and process which is effective ~o selectively impart a clear blue-bright or a clear light-yellow passivate film to zinc, zinc alloy, cadmium, - cadmium alloy, aluminium and magnesium surfaces which 10. provides for improved corrosion resistance. The present invention is further characterized by a process which is simple to control and operate and which is of efficient and economical operation.
The benefits and advantages of the first ~qpect 15. of the present invention are achieved in accorda~ce with the composition aspects thereof by providing an aqueous acidic treating solution containing as its esssential constituents hydrogen ions preferably to provide a solution pH of about 1.2 to about 2.5 which can be 20. conveniently introduced by mine.al acids such as sulphuric acid, nitric acid or hydrochloric acid; an oxidizlng agent of which hydrogen peroxide itself is preferred, preferably present in an amount of about 1 to about 20 g/l, iron and cobalt ions in an amount effective to 25. impart increased corrosion resistance to the treated substrate and preferably present ln an amount of about 0.02 to about 1 g/l to form a blue-bright or clear passivate film.
The treatlng solution contains an oxidizlng agent 30. in an amount effective to activate the metal surface and 1~:28~0() to form a passivate film thereon, and iron and cobalt ions present in an amount effective to activate the bath and to impart integral initial hardness to the passivate film. The treating solution may optionally 5. further co~tain cerium ions present in an amount effective to further activate the bath and to promote the formation of a clear light-yeIlow passivate film.
Additionally, the treating solution may optionally contain halide ions including fluoride, chloride and 10. bromide ions for increasing the hardness of the passivate film as well as one or more compatible wetting agents preferably in a small amount for achieving efficient contact with the substrate being treated.
The iron and cobalt ions are conveniently 15. introduced into the bath by way of bath soluble and compatible salts including sulphates~ nitrates, or halide salts. The concentration of the combined iron and cobalt ions to achieve appropriate actlvation of the treating bath is controlled within a range of about 20. 0.02 to about l g/l, preferablv within a range of about 0.1 to about 0.2 g/l. The iron and cobalt ions individ-ually are present in an amount of about 0.01 to about 0.5 g/l with individual amounts of about 0.05 to about 0.1 g/l being preferred.
25. When a passivate film is desired having a light-yellow appearance, the treating bath furthex contains cerium ions present in an amount effectlve to further activate the bath and to impart a clear yellowish colour, preferably an iridescent light-yellow colour to the 30. passivate film on the substrate treated. The cerium ions can be introduced in the form of any bath soluble 122~3~)0~) and compatible cerium salt including cerium sulphate (Ce(SO~)2 4H20); halide salts such as cerous chloride (CeC13 6H20~; or nitrate salts such as cerium nitrate (Ce(N03) 5H20), (Ce(N03)3(OH) 3H20). Usually, at 5. least some of the cerium ions are introduced into the bath in ~he tetravalent state to impart the character-istic yellow colour of the tetravalent cerium ion into the passivate film. Certain oxidizing agents such as hydrogen peroxide, act as a reducing agent under the 10. acid conditions prevalent in the bulk of the operatin~
bath and reduce some of the tetravalent cerium ions to the trivalent state. However, oxidizing agents such as hydrogen peroxide revert from a reducing agent to an oxidizing agent at the interface of the substrate 15. being treated due to the higher pH prevalent at the interface and oxidize at least some of the ~ivalent cerium ions to the tet~avalent scate which are de~osited in the film and impart the characteristic yellow colour thereto. When using such oxidizing agents as 20. hydrogen veroxide, accordingly, all of the cerium ions can, if desixed, be initially introduced into the operating bath in the trivalent state of which a portion are oxidized to the tetravalent state at the interface of the substrate. The passivate film usually contains 25. a mixture of trivalent and tetravalent cerium compounds and the intensity of the yellow colour of ~he film is dictated by the concentratlon of the tetravalent cerium compounds present. The cerium lons in addition to imparting a light-yellow colour to the passivate fllm 30. also improve the corrosion resistance of the treated 122800~

substrate. The cerium sulphate comDound, due to solub-ility difficulties, is ~referablY added to the bath in the form of an acid solution such as à dilute sulphuric acid solution containing the cerium sulphate dissolved 5- therein.
The concentration of cerium ions in the operating bath can range from about 0.5 up to about 10 g/l with concentrations of from about 1.0 to about 4.0 g/l being preferred. The concentration of cerium ions is 10. in part influenced by the magnitude of the yellow coating desired and higher concentrations of the cerium ions produce corresponding increases in the yellow colour of the passivate film.
Because o~ cost co~siderations, the cerium ions 15 n are preferably introduced as a commercially avai~able mixture of rare earth salts of metals in the lanthanide series which contains cerium compounds as the prlncipal component. One such commercially avallable material is a cerous chloride solution containing about 4~%
20- solids of which CeC13-6H20 predominates. The cerous chloride solution is derlved from rare earth oxide (REO) concentrate sold by Molycorp, ~nc. of White Plains, New York under product code 5310 containing a minimum of 99 percent total REO of which CeO2 is 96~, I.a203 is 25- 2.7%, Nd203 is 1% and Pr60 1 is 0.3%. A ceric sulphate solution is commercially available from the same source containing about 42% solids of which Ce(S04)2.H20 predominates and which is also prepared from product code 5310 containing other rare earth metal compounds in similar minor amounts.

122800~

The operating bath in accor~ance with this first aspect of the present invention can conveniently be prepared by employing a concentrate containing the active constituents with the exception of the cerium 5. ions and oxidizing agent which is ada~ted to be diluted with water t~ which the cerium ions, i.f employed, and oxidizing agent are separately added to form a bath containing the constituents within the desired concen-tration range. Similarly, replenishment of the bath 10. on a continuous or intermittent basis can be achieved employing a concentrate of the active constituents with the exception of the cerium ions and oxidizing agent which are individually added separately to the operating bath. Typically a bath make--up concentrate 15. can conta.in from about 0~5 to ahout 50 g/l of iron and cobalt i.OilS, halide ions up to about 20 g/l and a suitable surfaetant :In an amo~t up to about S g/l if employed. Such a make~up concentrate .is adapted to be diluted with about 96 volume percent water -to 20. which cerium ions, if employed, and a.n oxidizing agent are added to produce an operating bath containing the active constituents within the ranges specified. The oxidlzing agent such as hydrogen peroxide, for example, is separately introduced into the bath preferabl~ in a ~5. form commercially available containing from about 35 to 40 percent by volume hydro~en ~eroxlde.
As previously advised, ~he lo~ solublllty of cerlum sulphate makes it deslrable to lntroduce this constituent into the operating bath ln the orm of an 30. aqueous acidic solution. Normally, the use of cerium.

~2~300~
1.0 sulphate in the high concentrations necessary to form a concentrate with the remaining active constituents other than the peroxide constituent causes precipit-ation of the ceri um compound. Even when the cerium i.s introduced as a halide or nitrate salt, the pre-sence of sulphate ions in the concentrate employed introduced by the other constituents causes precipi.tation .
Accordin~ly, the cerium concentrate is pre-ferably formed as a separate addition cornponent and may comprise aqueous acidic solutions of cerous chloride or ceric sulphate having a cerium ion concentration of from about 200 to about 320 g/l and about 60 to 100 g/l, respectively. Such cerium concentrates may conveniently by comprised of the commercially available materials hereinbefore described available from Molycorp, Inc.
The treat inq bath contains hydrogen ions pre-ferably in an amount to provi.de a pH of about 1. . 2 to about 2 . 5 with a pH range of about 1. 5 to about

2.0 being preferred. Ac~dification of the operating bath ~o within the desired ph range can be achieved by a variety of mineral acids and organic acids such as sulphuric acid, nitric acid, hydrochloric acid, formic acid, acetic acid, or propionic acid of which sulphuric acid and nitric acid are preferred. The presence of sul.phate ions in the bath has been fourld beneficial in ach.ievirl(3 tlle dcsirecl p~.issiv.ltion o~' trle ~ub~.l rat~ c~ l c~lrl t~ rlt.r~ c.;l) lp~ r i~
acid ad.litioll or sulE)llat:(! 3alt~ Oe the o~:ller bcith constituents. Sulphate .ion collcelltrations can ranqt.?
in amounts up to l5 cl/l wi th conc(?ntra~iol)s of from about. 0.5 to about 5 ~/1 being prc?ferrt;?d~

.i~

~2Zc13000 The treating bath fur-the~ contains an oxidiz-ing agent or agents which are bath compatible of which peroxides including hydrogen peroxide and metal peroxides such as the al~ali metal peroxides s are preferred. Hydrogen peroxide itself of a commercial grade containing about 25% to about 60~
by volume peroxide constitutes the preferred material.
Other peroxides that can be employed include zinc peroxide. Additionally, ammonium and alkali metal persulphates have also been found effective as oxidizing agents~
The concentration of the oxidizing agent or mixture of oxidizing agents is controlled to achieve the desired surface appearance of the treated substrate. Typically, the concentration of the oxidizing agent can range from about 1 to about 20 g/l with an amount of about 3 to about 7 9/1 being preferred, calculated on a weight equivalent effectiveness basis to hydrogen peroxide.
As an optional but preferred constituent, the bath may contain halide ions including chlorine, bromine and fluorine ions which have been found to enhance the hardness of the passivate film on the treated subs~-rate.The halide ions or mixtures thereof can conveniently be introduced employing any of the alkali metal and ammonium salts thereof as well as salts of the metal ions hereinabove set forth. The concentration of the total halide constituent in the bath normally may ran~e up to about 8 gram~ per litre with concentrations of abollt 0.1 to about 2.5 g/l being kypical.
In the second fourth and fifth aspects of the invention it may be preferred that the concentration of the total halide constituent in the bath normally range up to about 2 grams per litre with concentra-tions of about 0.1 to about 0.5 g/l being typlcal.

12 ~ 22 8 00 ~

In addition to the foregoing, the use of a small effective amount of a variety of bath compatible wetting agents also provides beneficial results in the nature of the passivate film deposited. When employed, the wetting agent can be present in concentrations up to about 1 g/l with concentrations of about 50 to about 100 mg/l being preferred.
Wetting agents suitable for use in the treating bath include aliphatic fluorocarbon sulphonates avail-able from 3M under the trademark FLUORAD, such as, forexample, FLUORAD FC 98, which is a non-foaming wetting agent and its use at about 100 mg/l in the working bath improves the colour and hardness of the passivate film.
A second class of suita~le wetting agents is the sulpho-derivatives of succinates. An example of this class isAEROSOL MA-80 (trade mark) which is dihexyl ester of sodium sulphosuccinic acid and is commercially available from American Cyanamid Company. A third class of suit-able wetting agents is the sulphonates of naphthalene which are linear alkyl naphthalene sulphonates, such as PETRO BA (trade mark), for example, available from Petrochemical Company.
According to the gecond aspect of the present invention there is provided a treating solution and process which is effective to impart improved corrosion resistance to zinc, zinc alloy, cadmium and cadmium alloy, as well as aluminium and magnesium surfaces and to impart a desirable surface finish which can range from a clear bright to a light blue-bright appearance, which procegs is simple to control and operate and which is of efficient and economical operation. This and the 13 12 ~ ~0 ~
third to seventh aspects of the invention all utilize trivalent chromium ions.
The benefits and advantages of the second aspect of the present invention are achieved in accordance with the composition aspects thereof by providing an aqueous acidic treating solution con-taining as its essential constituents, chromium ions substantially all of which are present in the tri-valent state preferably at a concentration of from about 0.05 grams per litre (g/l) up to saturation, hydrogen ions preferably to provide a solution pH
of about 1.5 to about 2.2 which can be conveniently introduced by mineral acids such as sulphuric acid, nitric acid or hydrochloric acid, an oxidizing agent of which hydrogen peroxide itself is preferred, pre-ferably present in an amount of about 1 to about 20 g/l, and iron ions preferably present in an amount of about 0.05 to about O.S g/l e.g. in the ferric state in further combination with at least one additional metal ion selected from the group consisting of cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixture and mixtures thereof present in an amount effective to impart increased corrosion resistance to the treated substrate and to activate the bath and the formation of a chromium passivate film on the substrate treated.
As mentioned for the first aspect of the invention the solution may Purther optionally contain halide ions for impartin~ Initial hardness to t.hl? CO~lt: in~, as well as a wetting ac~ent.
In the second aspect o~ the invention whilst it is applicable in the same way as the first aspect, in the case of decorative zinc electroplatings, a further i22a~0~

14.

enhancement of the appearance of such substrates in addition to the corrosion resistance imparted is achieved by the passivate film which ranges from a clear bright to a light blue-bright appearance simu-lating that of a chromium deposit.
The treating solution contains an oxidizing agent in an amount effective to activate the hydrated trivalent chromium to form a chromate film on the metal surface, iron ions present in the operating bath in the ferric state at a concentration ranging from about 0.05 to about 0.5 grams per litre and at least one additional metal ion selected from the group con-sisting of cabalt, nickel, molybdenum, manganese, lanthanum and mixtures thereof present in an amount effective to impart integral initial hardness to the gelatinous chromate film.
The trivalent chromium ions can be introduced in the form of any bath soluble and compatible salt such as chromium sulphate (Cr2(S04)2), chromium alum (KCr(SO4)2), chromium chloride (CrC13), chromium bromide (CrBr3), chromium fluoride (CrF3), or chromium nitrate (CrN03). The trivalent chromium ions can also be introduced by a reduction of a solution containing hexavalent chromium ions employing an appropriate re-ducing agent of any of the types well known in the artto effect a substantially complete stoichiometric reduction of all of the hexavalent chromium to the trivalent 8tate.
The concentration of the trivalent chromium ions in the treating solution may range from as low as about 0.05 g/l up to saturation with quantities of about 0.2 to 2 g/l being preferred. Typically, the 8~00 15.

operating bath contains from about 0.5 to about 1 g/l trivalent chromium ions.
The treating solution further contains iron ions preferably present in an amount of about 0.05 to about 0.5 g/l with concentrations ranging from about 0.1 to about 0.2 g/l being preferred. The iron ions in the operating bath are predominantly in the ferric state due to the presence of the bath oxidizing agents although they can be added in the ferrous form. As in the case of the chromium ions, the iron ions can be added to the bath in the form of any bath soluble and compatible iron salt such as ferrous ammonium sulphate, ferric sulphate, ferric nitrate, or iron halide salts.
Of the foregoing, ferric sulphate comprises the pre-ferred material for economic reasons and because theuse of this salt also introduces the desired sulphate ions into the solution.
In addition to the iron ions, the bath further contains at least one additional metal ion selected from the group consisting of cobalt, nickel, molybdenum, manganese, lanthanum, as well as mixtures thereof. The foregoing metal ions or mixtures of metal ions are conveniently introduced as in the case of the iron ions, by way of bath soluble and compatible metal salts including the sulphates, nitrates or halide salts. For economic reasons, the lanthanum ions are preferably introduced not as a pure lanthanum compound, hut a~ a mixture of the rare earth salts of the metals of the lanthanide serie~, thereinafter designated as 16.

"l~nthanide mixture") which contains lanthanum compounds - as the predominant constituent. A commercially avai-lable lanthanide mixture which is suitable for use in the practice of the present invention is Lanthanum-Rare Earth Chloride, product code 5240, available from Molycorp, Inc. of White Plains, New York. This product has the general formula La-REG13-6H20 and is available as a solution containing about 55 to 60% by weight solids. The solution is prepared from a rare earth oxide (RE0) concentrate containing a minimum of 46% by weight to~al RE0 comprising about 6~ lanthanum oxide (La203), 21.5% neodymium oxide (Nd203), 1~
cerium oxide (CeO2), 7.5% praseodymium oxide (Pr6011) and 1% of residual RE0.
The presence of such other rare earth metals in the solution dies not appear to have any adverse effect at the low concentrations in which they are present and may further contribute to the activation of the treating solution in forming the pas3ivate film.
The concentration of the additional metal ions for appropriate activation of the treating bath is controlled to provide a concentration ranging from about 0.02 up to about 1 g/l with concentration of from about 0.1 to about 0.2 g/l being preferred.
The operating bath in accordance with this second a~pect of the invention can conveniently be prepared by employing a concentrate containing the active con~tl-tuents with the exception of the oxidizing agent which is adapted to ~e diluted w$th wat0r to form a bath con-taining the con~tituents within the de~ired concentra-tion range.

o Similarly, replenishment of the bath on a continuous or intermittent basis can be achieved employing a concentrate of the active constituents with the exception of the oxidizing agent which is added separately to the operating bath. Typically, a bath make-up concentrate can contain from about 10 to about 30 g/l chromium ions, about 0.5 to about lO g/l iron ions, from about 5 to about 50 g/l of at least one additional metal ion of the group consisting of cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixture or mixtures thereof, halide icns up to about 20 g/l and a suitable surfactant in an amount up to about 5 g/l if employed. Such a make-up concentrate is adapted to be diluted with about 98.5 volume percent water to produce an operating bath containing the active constituents within the ranges specified. The oxidizing agent such as hydrogen peroxide, for example, is separately introduced into the bath preferably in a form commercially available containing from about 35 to 40 percent by volume hydrogen peroxide.
According to the third aspect of the present invention there is provided a treating solution and process which is effective to impart a clear light-yellow passivate film to zinc, zinc alloy, cadmium,cadmium alloy, aluminium and magnesium surfaces which provides for improved corrosion resistance approaching or comparable to that heretofore obtained employing eonventional hexav-~Ient chromiutn passivating solutions. The present invention is further characterized by a process which is sitnple to control and operate and which is of efficient and economical operation.

'~-12~300~) 18.

The benefits and advantages of the third aspect of the present invention are achieved in accordance with the composition aspects thereof by providing an aqueous acidic treating solution containing as its essential constituents, chromium ions substantially all of which are present in the trivalent state prefer-able at a concentration of from about 0.05 grams per litre (g/l) up to saturation, hydrogen ions preferably to provide a solution pH of about 1.2 to about 2.5 which can be conveniently introduced by mineral acids such as sulphuric acid, nitric acid, or hydrochloric acid, an oxidizing agent of which hydrogen peroxide itself is preferred, preferably present in an amount of about 1 to about 20 g/l, and cerium ions present in an amount effective to activate the bath and the formation of a clear light-yellow chromium passivate film on the treated substrate.
In addition to the cerium ions in the treating solution, the solution may optionally and preferably further contain an additional metal ion selected from the group consisting of iron, cobalt, nickel, moly-bdenum, manganese, lanthanum, lanthanide mixtures as well as mixtures thereof to provide a further activation of the bath and passivate film formation. As mentioned 2~ for the earlier aspects of the invention the solution may optionally also contain halide ion~ for imparting harrdness to the coating in addition to a small amount of a w~tting agent. The cerium ions can be introduced with the treating solution in thi~ third aspect of the invention in the same manner as described for the first t - ~228!~0~
19 .

aspect of the invention.
In addition to the cerium ions, the bath may further optionally and preferably contain at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, lan-thanum, lanthanide mixtures as well as mixtures thereof.
Such metal ions may be introduced into the treating solution in this third aspect of the invention in the same manner as already described for the second aspect.
The operating bath in accordance with this third aspect of the invention can conveniently be prepared by employing a concentrate containing the active constituents with the exception of the cerium ions and oxidizing agent which is adapted to be diluted with water to which the cerium ions and oxidizing agent are separately added to form a bath containing the cons-tituents within the desired concentration range.
Similarly, replenishment of the bath on a continuous or intermittent basis can be achieved employing a concen-trate of the active constituents with the excepticn ofthe cerium ions and oxidizing agent which are indivi-dually added separately to the operating bath. Typically a bath make-up concentrate can contain from about 10 to about 80 g/l chromium ions, from about 0.5 to about 50 g/l of additional metal ions of the group consisting of iron, cobalt, nickel, molybdenum, mangane~e, lanthanum, lanthanide mixture, or mixtures thereof, halide ions up to about 20 g/l and a suitable ~ur~actant ln an amount up to about 5 g/l i~ employed. Such a maXe-up concen-trate is adapted to be diluted with about 96 volumepercent water to which cerium ions and an oxidizing o~
20.

agent are added to produce an operating bath containing the active constituents within the ranges specified.
The oxidizing agent such as hydrogen peroxide, for example, is separately introduced into the bath prefer-able in a form ccmmercially available containing fromabout 35 to 40 percent by volume hydrogen peroxide.
As previously advised, the low solubility of cerium sulphate makes it desirable to introduce this constituent into the operation bath in the form of an aqueous acidic solution. Normally, the use of cerium sulphate in the high concentrations necessary to form a concentrate with the remaining active constituents other than the peroxide constituent causes precipitation of the cerium compound. Even when the cerium is intro-duced as a halide or nitrate salt, the presence of~ulphate ion~ in the concentrate employed introduced by the other constituents causes precipitation.
Accordingly, the cerium concentrate is preferably formed as a separate addition component and may comprise aqueous acidic solutions of cerous chloride or ceric sulphate hav.ing a cerium ion concentration of from about 200 to about 320 g/l and about 60 to 100 g/l, respec-tively. Such cerium concentrates may conveniently be comprised of the commercially available materials hereinbefore-described available from Molycorp, Inc.
According to the fourth aspect of the present invention there is provided a treating solution and process which is effective to impart improved corrosion resistance to zinc, zinc alloy, cadmium and cadmium alloy, as well a~ aluminium and magnesium surfaces and to impart a decirable surface finish which can range from a clear bright to a light blue-bright to a yellow iridescent appearance, which produces a passivate film ~2;~300~
21.

of improved clarity and initial hardness, which process is simple to control and operate and which is of effi-cient and economical operation.
The benefits and advantages of the fourth aspect of the present invention are achieved in accordance with the composition aspects thereof by providing an aqueous acidic treating solution containing as its essential constituents, chromium ions substantially all of which are present in the trivalent state preferably at a concentration of from about 0.05 grams per litre (g/l) up to saturation, (and which can be introduced as discussed for the second and third aspects), hydrogen ions preferably to'provide a solution pH of about 1.2 to about 2.5 which can be conveniently introduced by mineral acids such as sulphuric acid, nitric acid, or hydrochloric acid, an oxidizing agent of which hydrogen peroxide itself i5 preferred, prefer-able present in an amount of about 1 to about 20 g/l, a bath soluble and compatible organic carboxylic acid present in an amount effective to impart initial hardness and clarity to the passivate film, the said organic acid having the structural formula:
(OH)a R (C~)b Wherein:
a is an integer from 0 to 6, b is an integer from 1 to 3, and R represents an alkyl, alkenyl, or aryl group containing from Cl to C6 carbon atoms, as well as the bath soluble and compatible salts thereof, and at least one additional metal ion selected ! ;~

22. 122800~

from the group consisting of iron, cobalt, nickel, molybdenum, manganese, lanthanum, cerium and lanthanide mixtures, as well as mixtures thereof present in an amount effective to activate the bath and forma-tion of a chromium passivate film of the desiredappearance on the substrate treated desirably imparting initial hardness to the gelatinous chromate film. As mentioned for the earlier aspects of the invention, the solution may further optionally contain halide ions for imparting additional hardness to the coating, as well as a wetting agent. In this fourth aspect of the invention whilst it is applicable in the same way as the first aspect in the case of decorative zinc elec-troplatings, a further enhancement of the appearance of such substrates in addition to the corrosion resistance imparted is achieved by the passivate film which ranges from a clear bright to a light blue-bright appearance simulating that of a chromium deposit or alternatively, a clear light-yellow appearance simulating that obtained by use of prior art hexavalent chromium solutions.
In addition, the bath further contains at least one additional metal ion selected from the group consisting or iron cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixtures and cerium, as well as mixtures thereof. The foregoing metal ions or mixtures of metal ions are conveniently introduced into the bath by way of bath soluhle and compatible metal salts including the sulphates, nitrates or halide salts, as discussed for the second and third embodiments and such materials as are discussed above for those aspects - 1~2~3~0~) 23.

can be and desirably are used in this aspect of the invention.
The concentration of the additional metal ions other than cerium ions for appropriate activation of the treating bath to produce a clear to blue-bright appearance is controlled to provide a concentration ranging from about 0.02 up to about 1 g/l with concen-trations of from about 0.1 to about 0.2 g/l being pre-ferred. While such metal ions can be used in concen-trations above 1 g/l, such as up to 10 g/l, the use ofsuch higher concentrations even in the absence of cerium ions tends to produce dull films of ayellow tint rather than the desired clear or light-blue films. For this reason, such higher concentrations are undesirable from an appearance standpoint.
A further essential constituent of the improved bath of the present invention comprises an organic carboxylic acid or salt thereof of the structural for-mula as hereinbefore set forth present in an amount effective to impart increased clarity and initial hardness to the gelatinous chromate film deposited.
The unexpected improvement in clarity of the film is particularly pronounced in connection with the light-yellow iridescent films produced from cerium ion con-taining solutions. The particular concentration or rangeof concentrations of the clar;ty/hardness agent will vary in proportion to molecular weight o~ the particular acid and/or metal salt employed with higher concentrations required for an equivalent effectiveness as the molecular weight of the additive agent increa~es. The particular - 122~

24.

concentration to achieve optimum clarification and hardness is also dictated to some extent by the con-centration of the other metal ions present in the bath with higher concentrations being used as the metal ion concentrations increase. Generally, the organic car-boxylic acid additive agent or metal salts thereof can be employed in amounts ranging from about 0.05 up to ~bout 4.0 g/l with concentrations of about 0.1 to about 1.0 g/l being usually preferred.
The additive can be introduced as the organic acid itself or as any bath soluble and compatible metal salt including the alkali metal salts, ammonium salts and salts of the several additional metal ions in the bath. ~or economic reasons, the organic acid is usually introduced as an acid or as the sodium or potassium salt thereof.
Within the scope of the strllctural formula as hereinabove set forth, organic carboxylic acids which have been found particularly suitable include malonic, maleic, succinic, gluconi~, tartaric and citric acids, of which succinic and or succinate salts have been found particularly effective.
The operating bath in accordance with this fourth aspect of the invention can conveniently be prepared by employing a concentrate contai*ing the active ingredients with the exception of the oxidizing agent and cerium ions, i~ used, which is adapted to be diluted with water to form a bath containing the cons-tituents within the desired concentration range.

3~ Similarly, replenishment of the bath on a continuous or intermittent basis can be achieved employing a l2zsoon concentrate of the active constituents with the exception of the oxidizing agent and cerium ions, if used, which is added separately to the operating bath. Typically, a bath make-up concentrate can contain from about lO
to about 80 g/l chromium ions, from about 1.0 to about 80 g/l of the organic carboxylic acid and/or salt additive agent, from about 5 to about 50 g/l of at least one additional metal ion of the group consisting of iron, cobalt, ~ickel, molybdenum, manganese, lantha-num, lanthanide mixture or mixtures thereof, halideions up to about 5 g/l if employed. Such a make-up concentrate is adapted to be diluted with about 98 volume percent water to produce an operating bath con-taining the active constituents within the ran~es specified. The oxidizing agent such as hydrogen peroxide for example, is separately introduced into the bath preferably in a form commercially available containing from about 35 to 40 percent by volume hydrogen peroxide.
The cerium ions, when employed, are preferably introduced in the form of an aqueous acid solution of cerous chlo-ride or ceric sulphate having cerium ion concent~ation of from about 200 to about 320 g/l and about ~0 to about 100 g/l, respectively. Such cerium concentrates may be conveniently comprised of the commercially available materials hereinbefore described available from Molycorp, Inc.
According to the fifth aspect of the preqent invention there is provided a treating solution which aims to reduce the severity of a problem of loss of oxidizing agent associated with p~ior art baths. Thus while improvements have been made in trivalent chromium ~ ., ~

12~800~

passivate compositions and processes to produce commercially acceptable passivate films, a continu-ing problem associated with such operating baths has been the relatively rapid loss of the peroxide-type oxidizing agent, particularly hydrogen peroxide,which is present as a necessary bath constituent to achieve acceptable passivate films. Such prior art operating baths also undergo a relatively rapid rise in pH necessitating careful control and addition of acids to maintain the pH level within the optimum opera-ting range. The progressive loss of the peroxide-type oxidizing agent, particularly hydrogen peroxide, is due in part to the presence of activating metal ions present in the solution as well as contaminating metal ions such as zinc or cadmium, for example, introduced by dissolution of the metal from substrates being treated which bend to catalyze a decomposition of the peroxide oxidizing agent. The progressive loss of the peroxide-type oxidizing agents occurs not only during processing but also during standing of the bath overnight and over weekends during plant shutdown. Typically, a fresh operating bath containing 3% by volume of a 35% solution of hydrogen peroxide on standing overnight will lose about 0.1%
by volume per hour of the hydrogen peroxide oxidizing agent while a used solution containing from about 2 to about 10 grams per litre of contaminating zinc ions will experience a loss of hydrogen peroxide at a rate as great as about 0.4% by volume per hour. It will be apparent from the foregoing that careful monitoring of the operating bath composition and frequent replenishment of the peroxide oxidizing agent is required to maintain optlmum bath efficiency which is not only costly but also time consuming.

i2~3000 Thus this fifth aspect of the present inven-tion aims to provide a treating solution and process which is effective to impart improved corrosion re-sistance to zinc, zinc alloy, cadmium and cadmium alloy, as well as aluminium and magnesium surfaces and to impart a desirable surface finish which can range from a clear bright to a light blue-bright to a yellow iridescent appearance, which produces a passivate film of improved corrosion resistance, hardness, durability, clarity and initial hardness, which provides a treating solution that is stabilized against rapid loss of the peroxide oxidizing agent and against a rapid rise in pH, which process is simple to control and operate and which is of efficient and economical operation.
The benefits and advantages of the fifth aspect od the present invention are achieved in accordance with the composition aspects thereof by providing an aqueous acidic treating solution con-taining as its essential constituents, chromiumions substantially all of which are present in the trivalent state preferably at a concentration of from about 0.05 grams per litre (g/l) up to satura-tion (and which can be introduced as discussed for the second to fourth aspects), hydrogen ions pre-ferably to provide a solution pH of about 1.2 to about 2.5 which can be conveniently introduced by mineral acids such as sulphuric acid, nitric acid, hydrochloric acid or the like, an oxidizing agent of which hydrogen peroxide itself is preferred, pre-ferably present in an amount of about 1 to about 20 g/1, a stabilizing additive comprising a mixture of l-hydroxy ethylidene-l,l diphosphonic acid and 1~28~)0n citric acid and the bath compatible and soluble salts thereof present in an amount effective to re-duce loss of the peroxide oxidizing agent and to stabilize the pH of the operating bath, and at least one additional metal ion selected from ~he group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures, and cerium as well as mixtures thereof present in an amount effective to activate the bath and forma-tion of a chromium passivate film of the desiredappearance on the substrate treated. As mentioned for the earlier aspects of the invention the solu-tion may optionally contain halide ions for imparting additional hardness to the coating, and optionally, a wetting agent. It may also incorporate a bath soluble and compatible silicate compound present in an amount effective to impart increased corrosion resistance and hardness to the passivate film e.g. in an amount of about 0.01 to about 5 g/l calculated as SiO2 as discussed in connection with the sixth aspect below. It may also incorporate a bath soluble compatible organic carboxylic acid present in an amount effective to further impart initial hardness and clarity to the passivate film as discussed in connection with the fourth aspect above.
In this fifth aspect of the invention whilst it is applicable in the same way as the first aspect in the case of decorative zinc electroplatings, a further enhancement of the appearance of such substrates in addition to the corrosion resistance imparted is achieved by the passivate film which ranges from a clear bright to ~' .~, 1%;~800~
29.

a light blue-bright appearance simulating that of a chromium deposit or alternatively, a clear light-yellow appearance simulating that obtained by use of prior art hexavalent chromium solutions.
A further essential constituent of the treating bath in accordance with the fifth aspect of the invention is the stabilizing agent comprising a mLxture of l-hydroxy ethylidene-l,1 diphosphonic acid and citric acid as well as the bath soluble and com-1~ patible salts thereof. The combination of the diphosphonic and citric acid constituents appears to provide a synergistic action in not only reducing the deco~position and rate of loss of the peroxide-type oxidizing agent but also in stabilizing the pH of the operating bath preventing a rapid rise as had here-tofore been experienced in prior art-type trivalent chromium passivation treating solutions. Typically, the two stabiliziny constituents are added in the acid form or as the alkali metal or ammonium salts thereof.
A commercially available material suitable for use is sold under the trade mark DEQUEST 2010 by Monsanto Chemical Company and comprises l-hydroxy ethylidene-l,l diphosphonate.
The diphosphonic acid or diphosphonate consti-tuent can be present in the operating hath in an amount of about 0.05 up to about 3 g/l with amount of about 0.1 to about 0.5 g/l being preferred. The citric acid or citrate constituent can be present in the ope-rating bath from about 0.1 to about 10 g/l with amounts of about 0.5 to about 1.5 g/l being preferred.
An optional but preferred constituent of the ~$
f- ~

~228130n treating bath comprises a silicate compound present in an amount effective to provide an improved corro-sion protection and hardness to the passivate film formed on the treated substrates. The silicates to be used and the amounts in which they should be used are discussed in more detail below in connection with the sixth aspect of the present invention.
In addition, the bath further contains at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures and cerium as well as mixtures thereof. The foregoing metal ions or mixtures of metal ions are conveniently introduced into the bath by way of bath soluble and compatible metal salts including the sulphates, nitrates, or halide salts, as discussed for the second to fourth aspects and such materials as are discussed above for those aspects can be and desir-ably are used in this aspect of the invention.
The foregoing metal ions or combinations thereof with the exception of cerium ions are em-ployed for producing a clear to a light-blue passivate film. When a light-yellow iridescent passivate film is desired, cerium ions are employed, preferably in combination with one or more of the other metal ions to produce a passivate film simula-ting in appearance the light yellow passivate films heretofore obtained employing hexavalent chromium passivating solutions which have been recognised and embodied is ASTM specifications in view of their characteristic colour and associated excellent corro-sion resistance. The cerium ions can be introduced .~

i22800() in the manner discussed above in connection with the first third and fourth aspects.
The concentration of the additional metal ions other than cerium ions for appropriate activation of the treating bath to produce a clear to blue-bright appearance should be controlled in the manner discussed in connection with the fourth aspect of the invention.
When the operating bath is to contain an organic carboxylic acid or salt thereof as discussed in connection with the fourth aspect of the present invention, the teaching there given should be followed. However, the presence of a silicate com-pound in the operating bath as discussed below in connection with the sixth aspect of the present invention has been found to also contribute to im-proved clarity of the passivate film, and accordingly, the use of the organic carboxylic acid addition agent is usually unnecessary when a silicate compound is employed in the bath.
The operating bath in accordance with this fifth aspect of the invention can conveniently be prepared by employing a concentrate containing the active constituents with the exception of the oxidizing agent and cerium ions, if used, which is adapted to be diluted with water to form a bath con-taining the constituents within the desired concentra-tion range. Similarlyr replenishment of the bath on a continuous or intermittent basis can be achieved employing a concentrate of the active constituents with the exception of the oxidizing agent and cerium ions, if used, which is added separately to the operating bath. Typically, a bath make-up concentrate can contain from about 10 to about 80 g/l chromium ions, from about 5 to about 50 g/l of at least one '.~

~ 228~)00 additional metal, ion of the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixture or mixtures thereof, halide ions up to about 50 g/l, from about 5 to about 30 g/l of a silicate compound, if used, calculated as SiO2; and a suitable surfactant in an amount up to about 5 g/1 if employed. Such a make-up concentrate is adapted to be diluted with about 98 volume percent water to produce an operating bath containing the active constituents within the ranges specified. The oxidizing agent such as hydrogen peroxide, for example, is separately introduced into the bath pre-ferably in a form commercially available containing from about 35 to 40 percent by volume hydrogen peroxide. The cerium ions, when employed, are pre-ferably introduced in the form of an aqueous acid solution of cerous chloride or ceric sulphate having cerium ion concentration of from about 200 to about 320 g/1 and about 60 to about 100 g/1, respectively.
Such cerium concentrates may be conveniently com-prised of the commercially available materials hereinbefore described available from Molycorp, Inc.
The foregoing trivalent chromium concentrate containing the metal ions and acid components in combination with an inorganic silicate compound has a tendancy to form precipitates during prolonged storage due to the high concentrations and acidic conditions present. Accordingly, such foregoing concentrates are normally diluted with water shortly after preparation to provide an operating bath containing the active constituents in the desired concentrations. Concentrates of substan-tially improved stability and prolonged shelf .

- 122800~

33.

storage life can be provided by the use of organic silicates as discussed below in connection with the sixth aspect in combination with the trivalent chro-mium ions, and optionally, halide ions and a wetting agent. Such stable concentrations conventionally contain from about 10 to about 80 g/l trivalent chromium ions, about 5 up to about 50 g/l of an organic quater-nary ammQnium silicate calculated as SiO2, halide ions up to about 50 g/l and a surfactant in an amount up to about 5 g/l. Such stable concentrate is adapted to be used in conjunction with a second concentrate containing the acid components, the additional metal ions in an amount of about 5 to about 50 g/l, up to 80 g/l of the organic carboxylic acid and/or salt additive agent if used. Such second concentrate can also optionally contain a portion or all of the halides and wetting agents if not employed in the first tri-valent chromium concentrate.
In the preparation of such a trivalent chromium/
silicate concentrate, the organic silicate is first diluted with water to the desired concentration range whereafter the trivalent chromium constituent is added along with the optional halide and wetting agent, if employed. A particularly suitable commercially avai-~ 25 lable organic silicate compound comprises QURAM 220 (trade mark) available from Emery Industries which comprises a quaternary amine silicate.
The diphosphonic acid and citric acid and/or diphosphonate and citrate stabilizing additive can be incorporated in any of the foregoing concentrates including the peroxide concentrate in an amount to 12Z800~

attain the desired concentration in the operating bath. Alternatively, the stabilizing additive can be prepared as a separate aqueous concentrate containing from about 30 to about 170 g~l of the diphosphonic/
diphosphonate compound in admixture with about 160 to about 500 g/l of the citric acid/citrate compound and added separately to the operating bath LO provide the desired working concentration in accordance with the limits hereinbefore specified, and typically,

4-5 g/l of the stabilizer concentrate. In accordance with a preferred practice, the stabilizing additive is incorporated directly in the chromium containing concentrate, the cerium ion concentrate in the case of a yellow passivate process, or in the second concentrate employed in conjunction with the organic silicate concentrate in amounts of about 3 to about 17 g~l diphosphonic acid/diphosphonate compound and about 16 to about 50 g/l citric acid/citrate compound.
As discussed above for the first to fourth aspects the treating bath can be applied to the sub-strate in a variety of ways and the process conditions described for these aspects can and desirably should be used for this fifth aspect of the present invention.
At the conclusion of the passivation treatment, the substrate is extracted from the treating solution and is dried such as by warm circulating air. Ordin-arily, such passivated substrates, particularly work pieces processed while supported on a work rack are characterised as having a uniform passivate film over the surfaces thereof requiring no further processing.
In the case of small work pieces which are treated ,~

122800~) in bulk such as in a rotating processing barrel, some damage such as scratches can occur in the passivate film during treatment and it is desirable in such instances to subject such work pieces to a post silicate rinse treatment (as discussed below as the seventh aspect of the present invention) to seal any such surface imperfections thereby substantially improving the corrosion protection of barrel-processed parts.
when such an optional post passivation silicate rinse treatment is employed, the substrate following the passivation treatment is preferably subjected to at least one or a plurality of water rinse steps usually at room temperature to remove residual pas-sivate solution from the surfaces thereof whereafter the substrates are contacted with the post silicate rinse solution in accordance with the teaching given below in connection with the seventh aspect of the present invention.
According to the sixth aspect of the present invention there is provided a treating solution which aims to reduce the severity of a problem of damage to the passivate of passivated workpieces during sub-sequent processing. Thus while improvements have been made in trivalent chromium passivate compositions and processes to produce commercially acceptable passivate films, such films as initially formed have been found in some instances to lack sufficient initial hardness to enable handling of the substrate through further work stages without encountering damage to the pas-sivate film. Additionally, such trivalent chromium passivate compositions and processes have also been found in some instances to lack optimum corrosion resistance, hardness and durability, and produce 0~

films which are somewhat cloudy and lack optimum clarity from an appearance standpoint.
Thus this sixth aspect of the present invention aims to provide a treating solution and process which is effective to impart improved corrosion resistance to zinc, zinc alloy, cadmium and cadmium alloy, as well as aluminium and magnesium surfaces and to impart a desirable surface finish which can range from a clear bright to a light blue-bright to a yellow iridescent appearance, which produces a passivate film of improved corrosion resistance, hardness, durability, clarity and initial hardness, which pro-cess is simple to control and operate and which is of efficient and economical operation.
lS The benefits and advantages of the sixth aspect of the present invention are achieved in accordance with the composition aspects thereof by providing an aqueous acidic treating solution con-taining as its essential constituents, chromium ions substantially all of which are present in the tri-valent state preferably at a concentration of from about 0.05 grams per litre (g/l) up to saturation (and which can be introduced as discussed for the second to fifth aspects), hydrogen ions preferably to provide a solution pH of about 1.2 to about 2.5 which can be conveniently introduced by mineral acids such as sulphuric acid, nitric acid, or hydro-chloric acid, an oxidizing agent of which hydrogen peroxide itself is preferred, preferably present in an amount of about 1 to about 20 g/l, a bath soluble and compatible silicate compound present in an amount effective to impart increased corrosion resistance and hardness to the passivate film (preferably present in an amount of about 0.01 to about S g/l calculated as SiO2), and at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures and cerium, as well as mixtures thereof present in an amount effective to activate the bath and formation of a chromium pas-sivate film of the desired appearance on the substrate treated. As mentioned for the earlier aspects of the invention, the solution may optionally contain halide ions for imparting additional hardness to the coating, and optionally a wetting agent. It may also incorpo-rate a bath soluble compatible organic carboxylic acid present in an amount effective to further impart initial hardness and clarity to the passivate film.
In this sixth aspect of the invention whilst it is applicable in the same way as the first aspeGt in the case of decorative zinc electroplatings, a further enhancement of th~ appearance of such sub-strates in addition to the corrosion resistance imparted is achieved by the passivate film which ranges from a clear bright to a light blue bright appearance simulating that of a chromium deposit or alternatively, a clear light-yellow appearance simulating that obtained by use of prior art hexa-valent chromium solutions.
A further essential constituent of the treating bath in accordance with the sixth aspect of the inven-tion is the silicate compound present in an amount effective to provide an improved corrosion protection and hardness to the passivate film formed on the treated substrate. The silicate compound may comprise a bath soluble and compatible inorganic or organic silicate compound as well as mixtures thereof which are preferably present in an amount of about 0.01 up to about 5 g/i calculated as SiO2 with concentra-.~

1~28~:10~

tions of about 0.1 to about 0.5 g/l being preferred.
When inorganic silicates are employed, concentrations above about 2 g/l in the operating bath are undesir-able because of the tendency of the silicate to form fine flocculent precipitates with the metal ions present in the bath under the acidic conditions present which contributes towards bath instability.
Organic silicates, on the other hand, provide for improved bath stability and are preferred for the formation of make-up and replenishment concentrates because of the improved stability and prolonged shelf life.
Inorganic silicates suitable for use in the practice of the present invention include alkali metal and ammonium silicates of which sodium silicate (Na2O.xSiO2(x=2-4) and potassium silicate (~2O.ySiO2 (y-3-5) are preferred for economical reasons. Organic silicates which can also be satisfactorily employed include quaternary ammonium silicates which include tetramethyl-ammonium silicate, phenyltrimethylammon;um silicate, disilicate and trisilicate, and benzyltri-methylammon~um silicate and disilicate. Such silicates meeting the purposes of this invention may be ex-pressed by the following general formula:
RoR':xsio2 yH2o Where R represents a quaternary ammonium radical substituted with four organic groups selected from the groups alkyl, alkylene, alkanol, aryl, alkylaryl or mixtures thereof, R' represents either R or a hydrogen atom,x equals 1 to 3 and y equals 0 to 15.

'q~.Z

l~Z1300~
39.

Such water soluble organic silicates including their synthesis and characterization are more fully described in the literature such as the article by Merrill and Spencer, "Some Quaternary Ammonium Sili-cates", published in the Journal of Physical and Colloid Chemistry, 55, 187 (1951). Similar silicates including typical syntheses thereof are also disclosed in United states Patent No. 3,993,548.
In addition, the bath further contains at least additional metal ion selected from the group consisting or iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures and cerium as well as mixtures thereof. The foregoing metal ions or mixtures of metal ions are conveniently introduced into the bath by way of bath soluble and compatible metal salts including the sulphates, nitrates, halide salts, as discussed for the second to fifth aspects and such materials as are discussed above for those aspects can be and desirably are used in this aspect of the invention.
The foregoing metal ions or combinations thereof with the exception of cerium ions are employed for producing a clear to a light-blue passivate film. When a light-yellow iridescent passivate film is desired, cerium ions are employed, preferably in combination with one or more of the other metal ions to produce a passivate film simulating in appearance the light-yellow passivate films heretofore obtained employing hexavalent chromium passivating solutions which have ~2~

been recognized and embodied in ASTM specifications in view of their characteristic colour and associated excellent corrosion resistance. The cerium ions can be introduced in the manner described above in connection with the first, third, fourth and fifth aspects.
The concentration of the additional metal ions other than cerium ions for appropriate activation of the treating bath to produce a clear to blue-bright appearance should be controlled in the manner dis-cussed in connection with the fourth and fifth aspects of the present invention.
When the operating bath is to contain an organic carboxylic acid or salt thereof as discussed in the fourth and fifth aspects of the present invention the teaching there given should be followed.
The presence of the silicate compound in the operating bath in accordance with this sixth aspect of the invention has unexpectedly been found to also contribute to improved clarity of the passivate film, and accordingly, the use of the organic carbo-xylic acid addition agent is not essential when a silicate i5 present in the bath in accordance with this aspect of the invention though it may be desirable.
The operating bath in accordance with this sixth aspect of the invention can conveniently be prepared by empioying a concentrate containing the active constituents with the exception of the oxidizing agent and cerium ions, if used, which is adapted to be diluted with water to form a bath containing the constituents within the desired concentration range. Similarly, replenishment of 'i"-~LZ281)0~) the bath on a continuous or intermittent basis can be achieved employing a concentrate of the active constituents with the exception of the oxidizing agent and cerium ions, if used, which is added sepa-rately to the operating bath. Typically, a bath make-up concentrate can contain from about 10 to about 80 g/l chromium ions, from about 5 to about 30 g/l of the silicate compound calculated as SiO2, from about 5 to about 50 g/l of at least one additional metal ion of the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixture or mixtures thereof, halide ions up to about 50 g/l and a suitable surfactant in an amount up to about 5 g/l if employed. Such a make-up concentrate is adapted to be diluted with about 98 volume percent water to produce an operating bath containing the active constituents within the ranges specified. The oxidizing agent such as hydrogen peroxide, for example, is separately introduced into the bath preferably in a form commercially available containing from about 35 to 40 percent by volume hydrogen peroxide.
The cerium ions, when employed, are preferably introduced in the form of an aqueous acid solution of cerous chloride or ceric sulphate having cerium ion concentration of from about 200 to about 320 g/l and about 60 to about 100 g/l, respectively. Such cerium concentrates may be conveniently comprised of the commercially available materials hereinbefore described available from Molycorp, Inc.

42 12Z8~10~) The foregoing trivalent chromium concentrate containing the silicate compound, metal ions and acid components has a tendency to form precipitates during prolonged storage due to the high concentra-tions and acid conditions present. Accordingly, such foregoing concentrates are normally diluted with water shortly after preparation to provide an operat-ing bath containing the active constituents in the desired concentrations. It has been further discovered in accordance with this sixth aspect of the present invention that concentrates of substantially improved stability and prolonged shelf storage life can be provided by the use of organic silicates of the types heretofore set forth in combination with the trivalent chromium ions and, optionally, halide ions and a wetting agent. Such stable concentrates conveniently contain from about 10 to about 80 g/l trivalent chromium ions, about 5 up to about 50 g/l of an organic quaternary ammonium silicate calculated as SiO2, halide ions up to about 50 g/l and a surfactant in an amount up to about 5 g/l. Such stable concen-trate is adapted to be used in conjunction with a second concentra~e containing the acid components, the additional metal ions in an amount of about 5 to about 100 g/l, up to 80 g/l of the organic carboxylic acid and/or salt additive agent if used. Such second concentrate can also optionally contain a portion or all of the halides and wetting agents if not employed in the first trivalent chromium concentrate.
In the preparation of such a trivalent chromium/

~r 43 12 2 8 00 ~

silicate concentrate, the organic silicate is first diluted with water to the desired concentration range whereafter the trivalent chromium constituent is added along with the optional halide and wetting agent, if employed. A particularly suitable commer-cially available organic silicate compound comprises Quram 220 available from Emery Industries which comprises a quaternary amine silicate.
This sixth aspect of the present invention further encompasses a novel concentrate composition suitable for make-up of the operating bath by dilu-tion with water containing as its essential consti-tuents trivalent chromium ions and an organic quaternary ammonium silicate which provides compati-bility and storage stability over prolonged timeperiods.
As discussed above for the first to fifth aspects the treating bath can be applied to the substrate in a variety of ways and the process conditions described for these aspects can and desirably should be used for this sixth aspect of the present invention.
At the conclusion of the passivation treatment, the substrate is extracted from the treating solu-tion and is dried such as by warm-circulating air.
Ordinarily, such passivated substrates, particularly work pieces processed while supported on a work rack are characterized as having a uniform passivate film over the surfaces thereof requiring no further processing. In the case of small work pieces which _.~ r ..: ..

1~2800~

are treated in bulk such as in a rotating processing barrel, some damage such as scratches can occur in the passivate film during treatment and is desirable in such instances to subject such work pieces to post silicate rinse treatment (as discussed below as the seventh aspect of the present invention) to seal any such surface imperfections thereby substanti-ally improving the corrosion protection of barrel-processed parts.
When such an optional post passivation silicate rinse treatment is employed, the substrate following the passivation treatment is preferably subjected to at least one or a plurality of water rinse steps usually at room temperature to remove residual passivate solution from the surfaces thereof where-after the substrates are contacted with the post silicate rinse solution in accordance with the teaching given below in connection with the seventh aspect of the present invention.
According to the seventh aspect of the present invention there is proved a treating process which addresses the same problem as the sixth aspect of the present invention namely that of damage to the passi-vate of the passivated work pieces during subsequent processing. Thus while improvements have been made in trivalent chromium passivate compositions and processes to produce commercially acceptable passivate films, such films as initially formed have been found in some instances to lack sufficient initial hardness to enable handling of the substrate through further work stages lZ;~300{~

without encountering damage to the passivate film.
Additionally, such trivalent chromium passivate compo-sitions and processes have also been found in some instances to lack optimum corrosion resistance, hardness and durability, and produce films which are somewhat cloudy and lack optimum clarity from an appearance standpoint.
Thus, this seventh aspect of the present invention aims to provide a process which is effective to impart improved corrosion resistance to zinc, zinc alloy, cadmium and cadmium alloy, as well as aluminium and magnesium surfaces and to impart a desirable surface finish which can range from a clear bright to a light blue-bright to a yellow iridescent appearance, which produces a passivate film of improved corrosion resistance, hardness, durability, clarity and initial hardness, which process is simple to control and operate and which is of efficient and economical operation.
The benefits and advantages of the seventh aspect of the present invention are achieved by a process which provides an aqueous acidic treating solution containing as its essential constituents, chromium ions substan-tially all of which are present in the trivalent state preferably at a concentration of from about 0.05 grams per litre (g/l) up to saturation, (and which can be introduced as discussed for the second to sixth aspects) hydrogen ions preferably to provide a solution pH of about 1.2 to about 2.5 which can be conveniently introduced by mineral acids such as sulphuric acid, nitric acid, or hydrochloric acid, an oxidizing agent 1228()0~) 46.

of which hydrogen peroxide itself is preferred, preferably present in an amount of about 1 to about 20 g/1, at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures and cerium as well as mixtures thereof, contacting the substrate with the said aqueous acidic solution for a period of time sufficient to form a passivate film thereon, and contacting for a period of at least about one second the passivated substrate with a dilute aqueous rinse solution containing a bath soluble and compatible silicate compound present in an amount effective to impart improved corrosion resistance and hardness to the passivate rilm, and thereafter drying the passivated silicate rinsed substrate.
The aqueous acidic solution may be as described in connection with any of the first to sixth foregoing aspects, and it may be used in the same way.
Following the passivation treatment, the subs-trate is preferably subjected to one or a pluralityof water rinse steps which may be at room temperature or at elevated temperatures whereafter the passivated substrate is contacted with a dilute aqueous silicate solution in the form of a final rinse step. The con-tact time of the passivated substrate with the silicatesolution may range for a period of at least about on~
second up to about one minute or longer and the silicate solution may range in temperature from about 50 up to about 150F (10 to 66C). Following the silicate rinse step, the substrate is dried such as by circulatin~
hot air, for example.

12X~o~
47.

The aqueous silicate rinse solution preferably contains as its essential constituent, a bath soluble and compatible inorganic or organic silicate compound as well as mixtures thereof present in an amount of about 1 to about 40 g/l, and preferably from about 5 to abou~ 15 g/l (calculated as SiO2). Inorganic silicates suitable for use in the practice of the present process include alkali metal and ammonillm silicates of which sodium silicate (~a20 xSiO2 (where x equals 2 to 4)) and potassium silicate (K20 ySiO2 (where y equals 3 to 5)) are preferred for economic reasons. Organic silicates which can also be satis-factorily employed include quaternary ammonium silicates which include tetramethylammonium silicate, phenyltri-methylammonium silicate, disilicate and trisilicate, and benzyltrimethylammonium silicate and disilicate.
Such silicates suitable for use in the present inven-tion have the following general formula:
RoR~:xsio2:y~2o where R represents a quaternary ammonium radical substituted with four organic groups selected from the groups alkyl, alkylene, alkanol, aryl, alkylaryl ox mixtures thereof, and ~' represents either R or a hydrogen atom, and x equals 1 to 3 and y equals O to 15.
Such water soluble organic silicates and their synthesis and characterization are more fully described in the literature such as the article by Merrill and Spencer, "Some Quaternary Ammonium Silicates", published in the Journal of Physical and Colloid Chemistry, 55, 187 (1951). Similar silicates and a typical synthesis - 122800~) 4~.

thereof are also disclosed in United States Patent No.
3,993,548.
Bec~use of the relatively higher cost of such organic silicates, the silicate rinse solution prefe-rably comprises inorganic silicates of which thepotassium and sodium silicates as hereinabove des-cribed are particularly preferred.
In addition to the silicate compound, the silicate rinse solution can optionally contain a bath soluble and compatible wetting agent for enhancing con-tact with the passivated surface present in conventional amount of about 0.05 up to about 5.0 g/l. The silicate rinse may also optionally include an emulsifiable organic substance such as an emulsifiable oil e.g.
present in an amount of from about 1 up to about 50 g/l to provide an oily film on the non-electroplated interior surfaces of ferrous substrates to provide temporary protection against rusting during further processing steps of the parts. When such parts have surfaces which are completely passivated such as, for example, zinc die castings, the use of the optional emulsifiable oil is not necessary.
Similarly, there are applications where an oil is not desired but temporary rust protection of interior unplated surfaces is still required. In these cases, a final rinse containing an alkali metal or ammonium nitrite such as sodium nitrite e.g. in an amount of about 0.1 to about 1.0 g/l may be used.
In addition a wetting agent or combination of wetting agents is preferably used in conjunction with the sodium nitrite e.g. in the amount of about 0.05 to about 5.0 g/l. The presence of silicates in the final rinse is also compatible with this treatment.

49~ 80 0 ~

The invention may be put into practice in various wavs and a number of specific embodiments will be described to illustrate the invention with reference to the accom-panyins examples.

5. Examples 1.1 and 1.2 relate to the first aspect of the invention which provides a chromium-like passivate through using a bath free of chromium ions.
Exam~les 2.1 to 2.8 relate to the second aspect of the invention which utilizes iron and cobalt as the lO.metallic activator and also incorporates trivalent chromium to produce bright bluish passivates.
Exam~les 3.1 to 3.5 relate to the third aspect of the invention which utilizes cerium as the metallic activator and again incorporates trivalent chromium 15.but this time gives a yellow passivate similar to hexa-valent chromium passivates.
Examples 4.1 to 4.3 relate to the four~l aspect of the invention which utilizes a carboxylic acid in baths of the same general types as s~own in the Examoles 20.of the second and third aspects. The carboxylic acid enhances the initial hardenino of the passivate.
Examples 5.1 to 5.8 relate to the fifth aspect of the invention which utilizes a bath soluble silicate in the passivate bath as well as trivalent chromium in 25.baths of the same general types as shown in the examples of the second and fourth asoects. The silicate enhances initial hardening of the passivate and corrosion resistance~
Examnles 6.1 to 6.5 relate to the sixth asPect of the invention which utilizes a mixture of citric acid 30.and a particular phosphonic acid to inhibit loss of oxidizing agent and increase of pH during use of the baths - ~ lZ28~0~

of the tvpes described in the second and fifth aspects.
Examples 7.1 to 7.3 relate to the seventh aspect of the invention which is a post passivation silicate rinse Process which produces hardenina of the passivate.

51. 122800~) ' EXAMPLE 1 1 A chromium-free passivating concentrate was prepared containing 12 g/l ammonium bifluoride, 12 g/l ferrous ammonium sulphate, 80 g~l cobalt sulphate, and S. 4.5~ by volume of concentrated sulphuric acid. An operatins bath was prepared comprising water to which 2%
by volume of the forego,ing passivating concentrate was added in addition to l.S volume percent hydrogen peroxide (38% concentration). The operating bath had a nominal 10. pH of about l.S to about 2Ø
Test panels carrying a bright electroplated zinc deposit which had been water rinsed after the electro-plating step and which were rinsed in a 5% by volume dilute nitric acid solution were immersed in the ~perating lS. passivating bath for a period of 20 seconds in the presence of mild agitation. Thereafter the test ~anels - were water rinsed and air dried. The ~es~ panels after drying were visually inspected and ~ere characterized as having a uniform clear bluish passi'vating film on the 20. surface the-reof. The operating bath had a nominal pH
of about l.S to about 2Ø

EXAMPLE 1.2 . .
In order to produce a li.ght yellow iridescent 25~ passivate film on z1nc electroplated test panels, cerium ions were introduced in a test operating bath containing 2% by vo~ume of the chromium-free passivatinq concentrate described in Example 1.1. 2~ by volume of a cerium sulphate concentrate comprising a 6% cerium sulphate (Ce 30] (S04)2) solution $n a dilute sulphuric acid solution and 1~5~ by volume of a hydrogen peroxide concentrate (3~%).
The normal pH of thecperating bath was about 1.~ ~o about 2Ø

., .
.~, 52 12~8~
The zinc test panels after plating, water rinsing and a nitric acid dip were immersed in the test solution in the presence of mild agitation for a period of 45 seconds. The treated test panels were water rinsed and air dried. A visual inspection of the surface of the test panel revealed a substantially uniform light-yellow iridescent passivate film.
EXAMPLE 2.1 An operating bath was prepared containing:
Ingredient Concentration, g/l -Cr2(So4)3 2.2 N~4HF2 .18 H2SO4 1.2 22 5.3 4S 4 0.25 SO4 .7H2O 1.6 * Ferrous Ammonium Sulphate = Fe(SO4) (NH4)2SO4 6H2O
Steel test panels were subjected to an alkaline, non-cyanide electroplating step to deposit a zinc plating thereon after which they were thor-oughly water rinsed and immersed with agitation in the above operating bath for a period of 20 seconds.
At the conclusion of the treatment, the passivated panels were warm water rinsed, and air dried. An inspection of the coating on the panels after drying revealed an exceptionally bright clear-bluish 3~ colouration with no haziness. Additionally, the coating exhibited the appearance of a bright nickel ,,~
~.

53 ~22800~
chromium electroplating and also exhibited excellent smear resistance on light finger-rubbing.
EXAMPLE 2.2 An operating bath was prepared containing:
Ingredient Concentration, g/l Cr2(SO4)3 5.6 NH~HF2 0.4 H2SO4 2.7 NH4S04 0.58 CoSO4 . 7H20 3.75 The operating bath of Example 2.2 is similar to that of Example 2.1 with the exception that the trivalent chromium, ammonium bifluoride, sulphuric acid, iron and cobalt constituents are all at higher concentrations. Zinc plated test panels treated with the bath of Example 2.2 produced results substantially equivalent to those obtained with the operating bath of Example 2.1 EXAMPLE 2.3 An operating bath was prepared containing:
Ingredient Concentration, g/l Cr2~SO4)3 3.0 4 2 0.24 2S4 1.54 4 4 0.25 4SO4 2.1 54 ~ ~ 2 ~o ~

*Nickel Ammonium Sulphate - NiSO4 (NH4)2SO4 6H2O

Zinc plated test panel treated with this operating bath under the same conditions as described in Example 2.1 were observed, after drying, to have a coating which was very bright with a clear bluish colouration and no haziness. The coating also ex-hibited good smear resistance on light finger rubbing.
1 EXAMPLE 2.4 An operating bath was prepared identical to that as set forth in Example 2.3 with the exception that 1.6 g/l of nickel sulphate was employed in place of 2.1 g/l of nickel ammonium sulphate. The zinc plated test panels treated in the manner as previously described in Example 2.1 employing the treating solution of Example 2.4 produced results substantially comparable to those obtained with the treating bath of Example 2.3 except that the coating had a slightly less bluish colouration.
EXAMP~ES 2.SA to 2.5E
. _ A series of passivating solutions were pre-pared for treating zinc plated steel test panels to evaluate their relative corrosion resistance to a 5 percent neutral salt spray after passivation. The composition of the solutions 5A, 5B, 5C and 5D are given in Table 1 below:

~28~)00 Table 1 Concentration, g/1 Ingredient 2.SA 2.5B 2.5C 2.5D
Cr2(SO4)3 3.0 3 0 3 0 3 0 4 2 0.24 0.24 0.24 0.24 H2SO4 1.54 1.54 1~54 1.54 H2O2 5.3 5.3 5.3 5.3 FeNH4S4 ~ 0.25 0.25 0.25 CoSO3 - - 1.6 NiNH4So4 - - - 2.1 Solution 2.5A contains only trivalent chromium ions; solution 2.5B additionally contains ferrous ions; solution 2.5C contains a combination of iron and cobalt ions while solution 2.5D contains a combination of iron and nickel ions.
In addition to the foregoing operating solu-tions, a traditional hexa~alent chromium passivating solution ~E~ample 2.SE) was prepared to serve as a control containing 0.63 g~1 sodium dichromate, 0.63 g/l a~nonium bifluoride, 0.01 g/l sulphuric acid, 0.65 g/l nitric acid. This solution is designated as solution 2.5E.
Duplicate sets of 3 inch by 4 inch (7.6 cms by 10.2 cms) steel panels were cleaned and zinc plated using a non-cyanide zinc plating electrolyte for fif-teen minutes at a plating current density of 20 amperes per square foot (ASF) (2.2 Amperes per Square decimi-ter (ASD))whereafter they were thoroughly rinsed. Each set of zinc plated test panels was then immersed in the '~
,....

56. 1228~0~

respective treating solution for a ~eriod of twenty seconds whereafter they were warm water rinsed, air-dried and thereafter allowed to age twenty-four hours prior to salt spray testing in accordance with ASTM standards.
5. The test panels were subjected to the five percent neu~ral salt spray for a total of forty-three hours.
For further comparati~e purposes, a duplicate set of zinc test panels without any passivation treatment was also subjected to the neutral salt spray test. The results lOo are set forth in Table 1.

NEUTRAL SALT SPRAY TEST RESULTS
. _ _ EX~MPLE TEST PE~CE~T WHITE PERCENT
PANEL CORRQSION, ~ RED RUST, Q
15.
-20SE Untleate~ 50 ~0 2~5A 5A - 4$ - 55 2.5B 5B ^ 10 - 15 0 20 2.5C 5C less than 2 o 2.5D 5D less than 10 0 2D5E SE ~5 ~ S5 0 ~ase~ on the foregoing test results it is apparent 25. ~ha~ the untreated ~inc ~lated test panel is a gross failure, the test panel treated with solution 2.5A is a failure; the test panels treated with solution 2.5B
are a marginal pass; the test panels treated with solutions 2.5C and 2.5D pass the test; and the test ~anel 30. ~reated with soluti~n 2.5E is a failure.

EXAMPLE 2.6 An operating bath was prepared containing:
Ingredient Concentration, g/l Cr2(SO4)3 3 0 4 2 0.24 H2SO4 1.54 N 4SO4 0.24 04 . H20 1. 0 Electroplated zinc test panels prepared in accordance with the procedure as set forth in Example 2.5 were immersed in the bath of Example 2.6 for a period of 30 seconds, warm water rinsed, air dried and allowed to age 24 hours prior to 5 percent neutral salt spray testing. For comparative purposes, zinc test panels were treated with the solutions 2.5A
and 2.5E of Example 2.5 and subjected to the same salt spray evaluation.
After 48 hours salt spray, an inspection of the several test panels revealed that the panels treated with the solution of Example 2.6 had superior corrosion resistance to that of the panels treated with solutions SA and 5E.

EXAMPLE 2.7 An operating bath was prepared containing:

:;

1~2~300~

Ingredient Concentration g/1 Cr2(SO4)3 3.0 4 2 0.24 H2S4 1.54 4 4 0.24 2 4 2 1.0 Electroplated zinc test panels prepared in accordance with Example 2.5 were immersed in the bath of Example 2.7 for a period of 30 seconds, warm water rinsed, air dried and allowed to age for 24 hours prior to 5 percent neutral salt spray testing. For lS comparative purposes, zinc test panels were treated with the solutions 2.5A and 2.SE of Example 2.5 and subjected to the same salt spray evaluation.
After 48 hours of salt spray test, an inspec-tion of the panels revealed that the panels treated with the solution of Example 2.7 had superior corrosion resistance to that of the test panels treated with solutions 2.5A and 2.5E.

EXAMPLE 2.8 An operating bath was prepared containing:

~22BO~)~

Ingredient Concentration, g/l Cr2(SO4)3 3.0 4 2 0.24 5 H2SO4 1.54 4 4 0.24 22 5.3 (NH4)4(NiMoo24H6)4 4H2 1.0 Electroplated zinc test panels prepared in accordance with the procedure described in Example 2.5 were immersed in the bath of Example 2.8 for a period of 30 seconds, warm water rinsed, air dried and allowed to age for 24 hours prior to a 5 percent neutral salt spray test. For comparative purposes, zinc test panels were treated with the solutions 2.5A and 2.5E of Example 2.5 and subjected to the same salt spray evaluation.
After 48 hours salt spray, an inspection of the panels revealed that the panels treated with the solution of Example 2.8 had superior corrosion resistance in comparison to the panels treated with solutions 2.5A and 2.5E.
A relative comparison of the test panels pre-pared in accordance with Examples 2.6, 2.7 and 2.8 revealed that the solution of Example 2.6 containing iron ions and Molybdic acid and the solution of Example 2.8 containing iron ions in combination with ammonium 6-molybdonickelate possessed superior corrosion resistance to the test panels treated with the operating solution of Example 2.6 cont-aining iron ions in combination with manganese ions.

- i228000 60.

The test panels treated in accordance with Examples 2.7 and 2.8 also possessed superior corrosion resistance to test panels treated with the test solution 2.5B of Example 2.5 containing only iron ions whereas the test panels treated with the solution of Example 2.6 con-taining both iron and manganese ions possessed corrosion resistance somewhat comparable to that of panels treated with solution 2.5B.

EXAMPLE 3.1 A concentrate 3.lA was prepared comprising an aqueous acidic solution containing 25 g/1 trivalent chromium ions introduced as chromium sulphate (KOREON
MF (trade mark) fro~ Allied Chemical Company), 12 g/l 15 ammonium chloride, 12 g/l ferrous ammonium sulphate and 4% by volume of concentrated sulphuric acid.
A second aqueous acidic concentrate 3.lB was prepared containing 60 g/1 tetravalent cerium ions introduced as Ce(SO4)2 4H2O and 5% by volume concen-20 trated sulphuric acid.
An operating bath was prepared comprising water containing 2% by volume concentrate 3.1A, 2% by volume concentrate 3.lB and 1.5% by volume of a 38Yo solution of hydrogen peroxide. Electroplated zinc test panels 25 immersed in this operating bath for 40 to 60 seconds had light-yellow iridescent passivate films on the surfaces thereof.

EXAMPLE 3.2 A concentrate 3.2A was prepared similar to con-~.

61 ~22~3~30~

centrate lA of Example 1 containing 25 g/l trivalent chromium ions, 20 g/l sodium chloride, 40 g/l ferric sulphate and 4% by volume concentrated sulphuric acid.
An operating bath was prepared comprising water containing 2% by volume concentrate 3.2A, 2% by volume Concentrate 3.1B of Example 3.1 and from 1.5-3~ by volume of a 38% solution of hydrogen peroxide. ~lectro-plated zinc test panels immersed in the operating bath produced results similar to Example 3.1.

EXA~PLE 3.3 A concentrate 3.3A was prepared similar to concentrate 3.lA of Example 3.1 except that 6~ by volume nitric acid was employed in place of 4 sulphuric acid.
An operating bath was prepared comprising water containing 2% by volume concentrate 3.3A, 2% by volume concentrate 3.lB of Example 3.1 and 1.5 - 3% by volume of a 38% solution of hydrogen peroxide. Electroplated zinc test panels immersed in the operating bath produced results similar to Example 3.1.

EXAMPLE 3.4 A concentrate 3.4A was prepared similar .o concentrate 3.2A of Example 3.2 except that 6~ by volume nitric acid was employed in place of 4~ by volume sulphuric acid.
An operating bath was prepared comprising water containing 2% by volume concentrate 3.4A, 2% by volume concentrate 3.lB of Example 3.1 and 1.5 - 3% by volume of a 38% solution of hydrogen peroxide. Electropiated zinc test panels immersed in the operating bath 62 1228t:)0~

produced results similar to Example 3.1.

EXAMPLES 3.5A to 3.5G
A series of seven aqueous test solutions were prepared each containing 1 g/l trivalent chromium ions, 1 g/l nitric acid, 1 g/l sulphuric acid, 7 g/l hydrogen peroxide and having a nominal pH of about 1.5.
To each test solution controlled additions of metal ions were made to evaluate the effect of such addi-tions on the colour, hardness and salt spray resis-tance of the passivate films produced on electro-plated zinc test panels immersed in each test opera-ting bath in the presence of mild agitation for a period of about 30 seconds and at a temperature of about 70F (21C).
The cerium ions were introduced as a CeC13 solution containing about 300 g/l cerium ions; the manganese ions were introduced as MnSO4 H2O; the ferric ions were introduced as Fe2(SO4)3 dissolved in a dilute sulphuric acid solution; the molybdenum ions were introduced as sodium molybdate dry salt; the lanthanum ions were introduced as an LaC13 solution containing about 85 ~/1 lanthanum ions; and the cobalt ions were introduced as cobalt sulphate. The test solutions are designated as Examples 3.5A to 3.5G and the concentration of metal ion additions are summarised in Table 2.

63 ~228000 METAL ION CONCENTRATION g/l Example 3.5A 3.5B 3.5C 3.5D 3.5E 3.5F 3.5G
Metal Ion CR+3 Ce+3 2 2 2 2 2 2 2 - O ~ 9 10 Fe+3 0.22 - - 0.08 0.08 Mo+6 _ - - 1.0 La+3 _ _ _ - 1.0 Co+2 _ _ _ - - - 0.13 15 Each test panel after immersion in the test operating bath was water rinsed and air dried and was visually inspected for colour and clarity. All of the test panels treated in solutions 3.5A to 3.5G were of substantially uniform light-yellow colour varying in clarity from a clear yellow film to films which were slightly hazy or hazy as set forth in Table 3. Each test panel after air drying was immediately tested for hardness of the passivate film by a light finger rubbing. The comparative hardness test results of the passivate film on the test panels treated in test solutions 3.5A to 3.5G is set forth in Table 3. It will be noted, that after a 24 hour aging of the test panels, the passivate film thereon became hard and rub resistant. The advantage of a passivate film which is hard immediately after air drying is that it can be handled for further processing without undergolng damage to the deposited film. Each test panel treated with test operating solutions 3.5A to 3.5G was also .~

64 1 % 2 800 O

subjected to a neutral salt spray for a period of 72 hours and the surface area, expressed in terms of a percentage, in which a white corrosion deposit was formed is also tabulated in Table 3.

TEST RESULTS

NEUTRAL SALT SPRAY
72 Hrs. - % White EXAMPLE CLARITY HARDNESS Corrosion _ .
3.5A Sl. haze Soft50 3.5B Sl. haze Soft100 3.5C Sl. haze Hard10 3.5D Haze Hard O
3.5E Sl. Haze Soft100 3.SF Clear Soft 2 3.5G Clear Hard 0 Based on the data as set forth in Table 2, from a clarity and hardness evaluation, Example 3.5G is a definite pass, Examples 3.5C and 3.5F are acceptable, which Examples 3.5A, 3.5B and 3.5E are less acceptable based on general appearance. From the standpoint of corrosion resistance, Examples 3.5D, 3.5F and 3.5G are definite passes, 3.5C a marginal pass, while Examples 3.5A, 3.5B and 3.SE are considered not acceptable based on ASTM corrosion standard specifications for a 72 hour neutral salt spray evaluation. It should be pointed out, however, that each of the test samples possess improved corrosion resistance in comparison 65 1 2~ ~ ~o ~

to an untreated electroplated zinc test panel and the passivate films which failed the 72 hour neutral salt spray test are nevertheless acceptable for less rigorous service exposures. The corrosion resistance provided by the Example 3.5G is substantially compara-ble to that attainable with conventional prior art hexavalent chromium passivate solutions of the types heretofore known. It will also be appreciated that variations in the types, combinations and concentra-tions of the metal ions contained in the test solu-tions can be made to optimize and improve the clarity, hardness and corrosion resistance of the test panels over the results as set forth in Table 3. The selec-tion of a 72 hour neutral salt spray condition is relatively severe and is generally employed for parts subjected to exterior exposure such as in automotive components. The 72 hour neutral salt spray test is normally applied to yellow hexavalent chromium pas-sivates although some specifications require only 48 hours while others require a 96 hour exposure~ The 72 hour test period was, accordingly, selected as being of average severity.

EXAMPLES 4.lA to 4.lG
A series of trivalent chromium containing con-centrates were prepared suitable for dilution with water to make up an operating bath in further combina-tion with an oxidizing agent and cerium or lanthanum ions as follows:

12Z~3~0~

CONCENTRATE 4.lA
INGREDIEN_ CONCENTRATION, g/l Cr+3 24 4 . H2O 25 Ferrous ammonium sulphate 12 Sodium fluoroborate 15 Succinic acld 25 Nitric acid (100~) 60 CONCENTRATE 4.lB
INGREDIENT CONCENTRATION, g/l Cr+3 24 NaCl 20 Ferrous ammonium sulpha~e 25 Sodium succinate 55 Nitric acid (100%) 60 CONCENTRATE 4.1C
INGREDIENT CONCENTRATION, 9/1 Cr+3 24 Ferric ammonium sulphate 50 Sodium succinate 55 NaCl 20 Nitric Acid (100%) 60 ....

67 12~8~)0~

CONCENTRATE 4.lD
INGREDIENT CONCENTRATION, g/l Cr+3 24 Ferric ammonium sulphate 50 Succinic acid 25 NaCl 20 Nitric acid (100%) 60 CONCENTRATE 4.1E
INGREDIENT CONCENTRATION, g/l Cr+3 24 Ferric ammonium sulphate 50 NaCl 20 Malonic acid 25 Nitric acid (100%) 60 CONCENTRATE 4.lF
NGREDIENT CONCENTRATION,g/l Cr+3 24 Fe2(SO4)3 30 NaCl 20 Gluconic acid 20 Nitric acid (100%) 60 ~800~

CONCENTRATE 4.1G
INGREDIENT CONCENTRATION, g/l Cr+3 24 Ferric ammonium sulphate 50 NaCl 20 Maleic acid 25 Nitric acid (100%) 60 EXAMPLES 4.2A to 4.2G
A cerium ion concentrate was provided contain-ing about 80 g/l ceric ions in the form of ceric sulphate in a dilute sulphuric acid solution. An oxidizing agent concentrate was also provided contain-ing about 35% hydrogen peroxide. A series of operating baths were prepared suitable for forming a yellow passivate film on a substrate each containing 2% by volume of the cerium ion concentrate, 2~ by volume of the oxidizing agent concentrate, and 2% by volume of one of the chromium concentrates 4.lA to 4.lG of Examples 4.lA to 4.lG.
Steel test panels were subjected to an alkaline, non-cyanide electroplating step to deposit a zinc plating thereon after which they were thoroughly water rinsed and immersed with agitation in each of the test operating baths for a period of abo~t 30 seconds maintained at a temperature of about 70F
(21C) and having a pH ranging from about 1.5 to about 2Ø At the conclusion of the passivation treat-ment, the passivated panels were warm water rinsed and air dried~ An inspection of the coating 69. 1 2 2 ~ 00 ~

on each of the test panels which had been immersed in each of the operating test solutions revealed the form-ation of a clear hard yellow passivate film.

5. EXAMPLES 4.3A to 4.3G
A lanthanum ion concentrate was provided contain-ing about 60 g/l lanthanum ions in the form of a solution of lanthanum chloride. An oxidizing agent concentrate was also provided containing about 35% hydroqen peroxide.
10. A series of operating baths were prepared su.itable for forming a blue-bright passivate film on a substrate each containing 2% by volume of the lanthanum ion concen-trate, 2% by volume of the oxidizi.ng agent concentrate, and 2~ by volume of one of the chromium concentrates 15. 4.lA to 4.lG of Example 4.1.
-~inc plated test panels as described .i..n Examnle ....... 4.2.were lmmersed under.the conditions described i~l Example 4.2.whereafter tl~ey-were warm water l~:insed ~ld a~r drie*. An inspec~i.on of the coa~ing on each of the 20. test.panels after drving revealed an exceptionallv . bright, clear, hard bluish coloured passivate film~
The yellow pass.ivated panels of Examples 4.2~, : 4.2B and 4~2C produced using operating baths containing, respectively,:concentrates 4.1A, 4.1B and 4~1C as herein-. 250 above described wère aged for at least 24 hours and subjected to neutral salt spray corrosion testing according to ASTM procedure B-117. The followina Table 4 indicates the corrosion resis~ance .results t~lat were obtained using these formulations:
30.

7~ -12 2 8 00 0 Table 4 Example Chromium Hours Neutral Salt S~rav Concentrate 72 96 4.2A 4.lA Clear with Clear with some dark some dark spots. sPots.
5- 4.2B 4.lB Clear with Clear with some dark some dark spots. s~ots.
4.2C 4.lC Clear with Some dark some dark snots - 1%
spots. white soots.
10 .
The above results show that panels treated with operating baths containing concentrates A, B, and C
passed the 96 hour salt spray test. Similar results were obtained with ~anels oroduced using the other 15. concentrates.

EX~MPLE 5.1 An ooerating bath suitable for de~ositing a yellow passivate film on a receptive substrate was orovided by 20. forming a trivalent chromium containing concentrate designated as "Concentrate 5.1A"having a comoosition as follows:
CONCENTRATE 5.lA
Inqredient Concentration q/l +3 25. Cr 50 Ferric ammonium sulohate 30 Sodium chloride 20 Nitric Acid (100%) 60 Succinic acid 20 30.
The trivalent chromium ions were introduced as Cr2(S04)3.

7 ' ~22800~) A cerium ion concentrate designated as "Concen-trate 5.lB"~as provided containing about 80 g/l ceric ions in the form of ceric sulphate in a dilute (about 5%) sulphuric acid solution. An oxidizing aaent concentrate 5. was also provided containing about 35% hydro~en ~eroxide.
A sodium silicate concentrate was also provided contain-ing 300 g/l sodium silicate calculated as SiO2.
A yellow passivate operating bath was prepared comprising water containing 2% by volume of Concentrate 10. 5.1A, 2% by volume of the cerium ion Concentrate 5.1B, 2~ by volume of the oxid~ng agent concentrate and 0.4%
by volume of the sodium silicate concentrate.
Steel test panels were subjected to an alkaline, non-cyanide electroplating step to deposit a 2inc plating 15. thereon after which they were thoroughly water rinsed and immersed with agitation in the passivate operating bath for a period of about 30 seconds at a temperature of about 70F (21 C) and at a pH ranging from about 1.5 to about 2Ø The test panels were thereafter ex~racted 20. from the operating bath and were dried with recirculating warm air.
The test panels after drving were visuallv inspected and were observed to have a very hard clear yellow passivate film. The test panels after aging for at least 25. 24 hours, were subject to a neutral salt spray corrosion test according to AST~ Procedure B-117. The test panels thus treated in accordance with the present process exhibited excellent salt s~ray resistance after ex~osure for a period of more than 96 hours.
30.

72. 1~8000 EXAMPLE 5.2 An operating bath suitable for depositing a vellow passivate film on a receptive substrate was provided by for~ing a trivalent chromium containing concentrate 5. designated as "Concentrate 5.2A" having a composition as follows:

CONCENTRATE 5.2A
Ingredient Concentrati-on g/l 10. Cr+3 50 Ferric ammonium sulphate 40 Sodium chloride 20 Nitric Acid (100~) 60 Sodium silicate (calculated as SiO2) 10 15. A yellow passivate operating bath was prepared comprising water containing 2~ by volume of Concentrate 5.2A, 2~ by volume of the cerium ion Concentrate-5.1B
of Example 5.1, and 2% by volume of the oxidizing aqent concentrate of Example 5.1.
20. Test panels prepared in accordance with the pro-cedure described in ExamPle 5.1 were immersed in the operating bath for a eriod of about 30 seconds at a temperature of about 70F (21C) and at a pH ranging from about 1.5 to about 2Ø The treated test panels were 25. dried with recirculating warm air and the dried panels were observed to have a very hard clear yellow passivate film. The test panels after aginq were subjected to a neutral salt spray corrosion test as aescribed in Example 5.1 and were observed to possess excellent salt spray 30. resistance after exposure for a period of more than 96 hours.

73. ~228~0~

EXAMPLE 5.3 An operatina bath suitable for depositing a vellow passivate film on a receptive substrate was provided by forming a trivalent chromium containinq 5. concentrate designated as "Concentrate 5.3A" having a composition as follows:

CONCENTRATE 5.3A
In~redient Concentration g/l 10. Cr+3 5~
Ferric ammonium sulphate 40 Nitric acid (100%) 60 Sodium chloride 20 An operating bath was prepared comprislng water 15. containina.2% by volu~.e of Concentrate 5.3A, 2~ by volume of the cerium ion containing Concentrate 5.lB
of Examnle 5.1, 2~ by volume of the oxidizing agent concentrate of Example 5.1, and 0.5% by vol~ne of the sodium silicate concentrate of Example 5.1.
20. Electroplated zinc test panels were treated in the operating bath in accordance with the procedure as described in Example 5.1 and after drying, were observed to have a good clear yellow passivate film.
The test panels also possessed good salt sprav 25. resistance evidencing excellent corrosion protection.

EXAM~LE 5.4 An operating bath suitable for depositinq a yellow passivate film on a receptive substrate was nrovided by 30. forming a trivalent chromium containing concentrate 74, 1~Z8~0~

incorporating a quaternarv amine silicate designated as "Concentrate 5.4A" having a composition as follows:

` CONCENTRATE 5.4A
5. Ingredient Concentration g/l C +3 Quaternary amine silicate* 15 Sodium chloride 15 * Quram 220, calculated as SiO2.
10. The trivalent chromium containing Concentrate 5.4A was subjected to prolonged storage and was observed to possess excellent stability over prolon~ed storage times.
In addition, a second concen~rate desianated as 15. "Concentrate 5.4R" was ~repared having a composition as follows:

CONCENTRATE 5.4B
Ingredient Concentration g/l 20. Nitric Acid (100~) 60 Sulphuric acid (100%) 30 Ferric sulPhate 25 Ceriurn chloride 120 An operating bath was prepared comprising water 25. containing 2% by volume of Concentrate 5.4A, 2% by volume of Concentrate 5.4B and 2% by volume of the oxidizing agent concentrate as described in Example 5.1.
Zinc plating test panels were contacted with the operating bath in accordance with the procedure 30. and under the conditions as described in Example 5.1 12i~8~0~
whereafter the test panels were dried with recircula-ting warm air. The test panels were observed to have an excellent hard and clear yellow passivate film and possess excellent salt spray resistance showing zero white corrosion formation after exposure to a neutral salt spray test for a period of 96 hours.

EXAMPLE S.5 A second series of electroplated zinc test panels were treated with the operating bath as pre-viously described in Example 5.4 under the same conditions whereafter the test panels were water rinsed and thereafter post-rinsed for a period of 30 seconds in an aqueous solution at room temperature containing 10 g/l sodium silicate calculated as SiO2.
The panels after the post rinse were extracted and dried with warm air.
The test panels were inspected and observed to possess a very hard clear yellow passivate film.
After aging, the test panels were subjected to a neutral salt spray corrosion test and exhibited excellent salt spray resistance after exposure of 96 to 140 hours. These tests also showed that when a post silicate rinse treatment is employed, the presence of some nitrate ions in the passivate operating bath is desirable to avoid the formation of some haze, in some instances, in the passivate film as a result of the post dip operation.

EXAMPLE 5.6 An operating bath suitable for depositing a blue-bright passivate film on a receptive substrate was 76. 12 2 8~0 0 provided by forming a concentrate designated as "Concentrate 5.6A" having a composition as follows:

CONCENTRAT~ 5.6A
5. Ingredient Concentration g~l Nitric acid (100%) 30 Sulphuric acid (100~) 20 Succinic acid 20 La~RE-C13 80 10. A passivate operating bath was prepared comDrising water containing 3% by volume of Concentrate 5.4A of Example 5.4, 3% by volume of Concentrate 5.6A and 3~
by volume of the oxidizing agent concentrate of Example 5.1.
15. Electroplated zinc test panels were treated with the operating bath in accordance with the procedure as pr~viously described in Example 5.1 and the test panels after drying were observed to possess an excellent blue-bright passivate film. The test panels also possessed 20. excellent corrosion resistance as shown by the ab-sence of white corrosion after being subjected to a neutral salt spray corrosion test for a period of from 48 up to 72 hours.

25. EXAMPLES 5.7.1 and 5.7.2 A trivalent chromium containing concentrate was prepared desi~nated as "Concentrate 5.7A" havin~ a composition as follows:

30.

77, 12 2 800 CONCENTRATE 5.7A
Inqredient C-oncentration -g/l Cr 30 Sodium chloride 10 5. Sodium silicate (Calculated as SiO2) 10 An operating bath (Example 5.7.1) suitable for depositing a yellow passivate film on a receptive substrate was prepared by emploving 2% by volume of Concentrate 5.7A, 2% by volume of Concentrate 5.4B of 10. Example 5.4 and 2% by volume of the oxidizing agent concentrate of Example 5.1. On the other hand, an operating bath (Examle 5.7.2) suitable for depositing a blue-bright passivate film was achieved by employing 2% by volume of Concentrate 5.7A, 2~ by volume of 15. Concentrate 5.6A of Example 5.6 and 2% by volume of the oxidizing agent concentrate of Example 5.1.
Test panels treated in accordance with the pro cedure described in Example 5~1 evidenced excellent passivate films and exhibited excellent corrosion pro-20. tection.

EXAMPLE 5.8 An operating bath suitable for depositinq ablue-bright passivate film on a rece~tive substrate 25. was provided by forming a trivalent chromium containing concentrate designated as "Concentrate 5.8A" havina a composition as follows:

1228~)00 78.

CONCENTRATE 5.8~
Inqredient Concentration g/l _ Cr 30 Sodium chloride 13 5. Sodium gluconate 10 Quaternarv amine silicate* 15 *Quram 220, calculated as SiO2 A second concentrate designated as "Concentrate 5.8B" was provided having a composition as follows:
10.
CONCENTRATE 5.8B
Ingredient Concentration g-/l Nitric acid (100~) 60 Sulphuric acid (100%) 30 15- A12(S4)3 30 An operating bath was prepared comprising water containing 3% by volume of Concentrate 5.8A, 3% by volume of Concentrate 5.8B and 3% by volume of the oxid-izing agent concentrate of Example 5.1.
20. Electroplated zinc test panels were treated in accordance with the procedure described in Example 5.1 and after drying were observed to have a clear bright passivate film. Testing of such panels in neutral salt spray corrosion tests evidenced a corrosion resistance 25. of at least 12 up to 24 hours.

EXAMPLE 6.1 . .
An operating bath suitable for depositing a yellow passivate film on a receptive substrate was 30. provided by forming a trivalent chromium concentrate designated as "Concentrate 6.lA" havin~ a composition as follows:

79- 12 ~ 8 CONCENTRATE 6.lA
Ingredient Concentration g/l Cr 30 Quaternary Ammonium silicate 15 5. NaC1 15 The trivalent chromium ions were introduced as Cr2(S04)3 while the silicate compound was introduced as Quram 220 from Emery Industries.
A cerium ion concentrate designated as "Concen-10. trate 6.1B" was provided having a composition as follows:

CONCENTRATE 6.lB
Ingredient Concentration q/l .
HN03 (100~) 60 15. H2~04 (100~) 30 Fe23S04)3 25 Ce 120 The cerium ions were introduced by way of a cerium chloride solution containing about 300 g/l Ce 3 20. ions.
In addition, an oxidizing agent concentrate was provided containing about 35% hydrogen peroxide.
A series of one litre operatina baths were ~repared comprising 3% by volume Concentrate 6. lA, 3~ bv volume 25. Concentrate 6.lB and 3% by volume of the oxidizina agent concentrate. In order to simulate an aqed ooeratinq bath used for oassivation of zinc workpieces, 1 g/l o r zinc dust was dissolved in each test solution.
One suc~ test solution without fur;her ad~iti ~ was desisnated 30. as test solution ~.1.1 and served as the contr~l sa~ple. To a second test solution desianated as 6.1.~ /1 of citric acid and 0;4 ~/1 of l-hydrox~v ethylidene-l,1 diphosphonate ~Nest 2010) was added as a stabilizing agent. To a third test solu~ion desi~nated 80. 1228~00 as 6.1.3, 1 g/l of citric acid and 0.08 g/l of 1-hydroxy ethylidene-l,l diphosphonate (Dequest 2010) was added.
Each test solution was su~jected to agitation at 5. room temperature to simulate typical commercial practice.
The pH at start and finish and the peroxide concentration measuredin terms of volume percent of 35% hydroqen peroxide concentrate remaining in the bath was analyzed over a one-day period. The results are as follows:
10. H`YDROOEN PEROXIDE CONCENTRATION AND cpH
Test Sample Example 6.1.1 6.1.2 6.1.3 Time H22 pH H22 PH H2G2 ~H
Start 2.56% 1.6 2.95~1.6 3.05% 1.4 15. After 3,5 2.39% - 2,92% - 2.84%
hours After 21 Oq83% -- 1.72% - 2,37 1.7 hours After 26 0.50% 2.5 1.42%1.8 hours 20. From the results as set forth in the foregoing table, it is apparent that control sample 6.1.1 devoid of any stabilizing agent rapidly lost the peroxide - oxidizing agent which should be present at a concentration of at least 2~ by volume to maintain proper passivation 25. treatment. An almost complete replenishment of the oxidizing agent in Sample 6.1.1 would therefore be necessary after a period of about one day. In contrast, sample 6.1.3 exhibited only a small loss of peroxide after 21 hours while sample 6.1.2 containina a lesser 30. quantity of Dequest 2010 in combination with 1 ~/1 of 8~ 2~00 citric acid also exhibited a sur~rising superiority in peroxide stability over the control sam~le 6.1.1.
The stabilization of pH is also evident from the data set forth in the fore~ing table. Control sam~le 5. 6.1.1 rose to a pH level of 2.5 after 26 hours which would have necessitated the addition of acid to the operating bath to maintain the pH within the ~referred operating range of 1.5 to 2Ø On the other hand, both samples 6.1.2 and 6.1.3 were substantially stable and 10. remained within ontimum pH range over the test duration.

EXAMPLE 6.2 An aqueous stabilizer concentrate was prepared containing 570 g/l citric acid and 110 ~ hydroxy 15. ethylidene-l,l-diphosphonate (Dequest 2010~. These operating solutions were prepared as described in Example 5.1 containing 3% by vol~me Concentrate 6~lA, 3% by volume Concentrate 6.lB, 3% by volume of the oxidizing concentrate and 1 g/l zinc dust for agln~ the 20. baths. A control sample designated 6.2.1 devoid of any stabilizing agent had an initial peroxide concentrat-ion of 3% but after standinq for a period of 18 hours under the conditions of Example 6.1 had a residual peroxide concentration of only 1.05% necessitating 25. replenishment. A second test solution desi~nated as

6.2.2 was stabilized by the addition of 2.5 millilitres /litre of the stabilizer concentrate and had an initial peroxide concentration of 3~ and after a period of 18 hours had a residual neroxide concentration of 2.43 30. percent.

8~
i22800~:) EXAMPLE 6.3 In order to evaluate the effectiveness of the peroxide and pH stabilizing agent of this aspect of the present invention under actual commercial operation, 5. the stabilizer concentrate as defined in Example 6.2 was employed for stabilizing a trivalent chromium passivate solution of a composition similar to the operating bath of Example 6.1 containing trivalent chromium ions, iron and cerium ions to provide a pH within the range of about 10. 1.5 to about 2.0 at a temperature of about 70F (21 C) and containing hydrogen peroxide as the oxidizing agent.
Under normal operation, in the absence of the stahilizer agent, the commercial operating bath necessitated a replen-ishment of the peroxide oxidizing agent with the addition 15. of 3% by volume of a 35% hydrogen peroxide concentrate each morning at the commencement of operation as well as the addition of another 1% by volume of the peroxide oxidizing concentrate after about 4 hours operation to maintain the bath at a minimum of 2~ by volume oxidizin~
20. agent.
By the addition of 1 litre of the stabilizer con-centrate per one hundred gallons of the operating bath, the replenishment of the peroxide oxidizing concentrate was reduced to only a 1% by volume replenishment each 25. operating dav and only a 2% by volume replenishment after standing over the weekend to restore the bath to a proper operating condition.
Additionally, the addition of the stabilizer con-centrate to the operating bath further stabilized the 30. operating p~ over the six day test period wherein the pH

83. 12 2 8 ~o~

remained substantially constant avoiding the necessity of acid addition to control pH. In contrast, the same commercial operating bath without any of the stabilizer concentrate necessitated frequent monitoring of pH and 5. periodic addition o acid to maintain the pH within the desired range of 1.5 to 2Ø
Bright zinc electroPlated parts processed employing the foregoing commercial operating bath after aging for at least 24 hours were subjected to a neutral salt spray 10. corrosion test according to ASTM Procedure B-117. The excellent corrosion resistancè of the yellow passivate film was evidenced by the absence of white corrosion on the parts after 96 hours salt spray testing.

15. EXAMPLE 6.4 The stabilization of a commercial operating bath of a composition and employing the procedure as described in Example 6.3 was achiev~d by preparing an aqueous stabilizer concentraté containing from about 30 20. to about 170 g/l of l-hydroxy ethylidene-l,l diphosphon-ate (Dequest 2010) in admixture with about 160 to about 500 g/l of citric acid. The stabilizing concentrate was added to the commercial operating bath to provide an operating concentration of the l-hydroxy ethYlidene-l,l 25. diphosphonate in an amount of about 0.05 to about 3 g/l and an operating concentration of the citric acid constituent of about 0.1 to about 10 g/l. Results obtained are similar to those as described in Example 6.3.

30.

84. 1228~00 EXAMPLE 6.5 . _ _ An operating bath suitable for depositing a yellow passivate film on a receptive substrate was provided by forming a concentrate designated as 5. "Concentrate 6.5A" having a composition as follows:

CONCENTRATE 6.5A
Ingredient Concentrat-ion g/l HN03(100~) 60 10. H2S04 r100%) 30 Fe2(S04)3 - 25 FeC13 5 Diphosphonate* - 8.5 Citric acid 36 15. Ce 120 *Dequest 201C
An operating bath was prepared comprising 3% by volume of the chromium ion concentr~te 6.lA o~ Example 6.1, 3~ by volume of concentrate 6.~A and 3% bv volume 20. of the oxidi~ing agent concentrate containing about 35%
hydrogen peroxide.
Steel test panels were subjected to an alkaline non-cyanide electroplating step to deposit a zinc plating thereon after which they were thoroughly water 25. rinsed and immersed with agitation in the passivate operating bath ~or a period of about 30 secon~s at a temperature of about 70F (21 C) and at a pH ranginq from about 1.5 to about 2Ø The test panels were there-after extracted from the o~erating bath and were dried 30. with recirculating warm air.

~ 22800~:) 85.

The test panels after drying were visually inspected and were observed to have a uniform clear yellow passivate film thereover. The small addition of ferric chloxide to the operating bath provides an 5. improvement in the colour intensity of the yellow passivate film in comparison to that obtained employing the passivate operating bath of Example 6.1.
The test panels after aging were subjected to a neutral salt spray test in accordance with the pro-10. cedure described in Example 6.3 and similar results wereobtained.

ExAMæLE 7.1 An operating bath suitable for depositing a 15. yellow passivate film on a receptive substrate was made up as follows: A trivalent chromium containing concentrate designated as "Concentrate 7.1A" having a compositlon was first made up as follows:

20. CONCENTRAIE7.lA
Ingredient Concentration g/l Cr . 25 - Ferric ammonium sulphate 30 Sodium chloride 20 25. Nitric acid (100%) 60 Succinic acid 20 A cerium ion concentrate 7.lB was provided con-taining about 80 g/l ceric ions in the form of ceric sulphate in a dilute (about 5~) sulphuric acid solution.
30. An oxidizing agent concentrate was also provided con-86. 1228~0~

taining about 35~ hydrogen peroxide.
A yellow passivate operating bath wasprepared com~rising water containing 2% by volumè of Concentrate7.lA, 2% by volume of the cerium ion concen-5. trate7.lB and 2~ by volume of the oxidizing agentconcentrate 7,lC.
An aqueous silicate rinse solution was ~rovided containinq 10 q/1 sodium silicate calculated as SiO2.
Steel test ~anels were subjected to an alkaline, 10. non-cyanide electroplating step to deposit a zinc plating thereon after which they were thoroughly water rinsed and immersed with agitation in the passivate 02eratina bath for a period of about 30 seconds at a temperature of about 70F (21C) and at a pH ranging from about 1~5 15. to about 2Ø The test panels were extracted from the operating bath, subjected to a tap water rinse and were thereafter contacted with the silicate rinse solution for about 30 seconds at a tem~eratulre of about 70F
(21 ~). The silicate rinsed-test ~anels were thereafter 20. extracted from the rinse solution and were dried with recirculating warm air.
The test panels after drying were visually ins~ected and were observed to have a very hard clear yellow ~assivate film. The test ~anels after aging for 25. at least 24 hours, were subjected to a neutral salt spray corrosion test according to AST~ Procedure B-117.
The test panels treated in accordance with the present process exhibited excellent salt sprav resistance after exposure for a period of more than 96 hours.
30.

12Z8~0~) 87.

EXAMPLES 7.2.1 to 7.2.14 A series of trivalent chromium containina concentrates was prepared suitable for dilution with water to make up an operating bath in further combination 5, with an oxidizing agent and cerium or lanthanum ions as follows:

CoNcENTRATE 7.2A

10. Ingredient Concentration, g/l Cr 24 Ferrous ammonium sulFhate 12 15. Sodium Fluoroborate 15 Succinic acid 25 Mitric acid (100%~ 60 CONCENTRATE 7.2B
Ingredient Concentration, g/l Cr 24 NaCl 20 25. Ferrous ammonium sulphate 25 Sodium succinate 55 Nitric acid (100%) 60 122800~) CONCENTRATE 7.2C
Ingredient Concentration, g/l Cr+3 24 5- Ferric ammonium sulphate 50 Sodium succinate 55 NaCl 20 Nitric acid (100%) 60 10.
CONCENTRATE 7.2D
Ingredient Concentration, g/l Cr+3 24 15. Ferric ammonium sulphate 50 Succinic acid 25 NaCl I 20 Nitric acid (100%) 60 20.
CONCENTRATE7.2E
Ingredient Concentration, g/l Cr~3 24 25. Ferric ammonium sulphate 50 NaCl 20 Malonic acid 25 Nitric acid (100~) 60 30.

89. ~28000 CONCENTRATE 7.2F
Ingredient Concentration, g/l Cr~3 24 5. Fe2(S04)3 30 NaC1 20 Gluconic acid 20 Nitric acid (100%) 60 10 . __ .
CONCENTRATE 7.2G
. . _ Ingredient Concentration, g/l Cr+3 24 15. Ferric ammonium sulphate 50 NaC1 20 Maleic acid ~ 25 Nitric acid (100%) 60 20.
A cerium ion concentra.~ was ~rovided containing about 80 y/l ceric ions in the form of ceric sulphate in a dilute sulphuric acid solution. An oxidizing agent con~ntrate was also provided containing about 35% hydrogen 25. peroxide. A series of operating baths (Exam~les 7.2.1 to `1.2.7) were prePared suitable for forming a vellow passivate film on a substrate each containina 2% by volume of the cerium ion concentrate, 2~ by volume of the oxidizing agen.t concentratel and 2% by volume of 30. one of the chromium concentrates 7.2A to 7.2G resDectively.

90. 122800~

A lanthanum ion concentrate was provided containing about 60 g/l lanthanum ions in the form of a solution of lanthanum chloride. An oxidizing agent concentrate was also provided containing about 35%
5. hydrogen peroxide. A series of ooerating baths (Examples

7.2.8 to 7.2.14) were prepared suitable for fol~ing a blue-bright passivate film on a substrate each containing 2% by volume of the lanthanum ion concentrate, 2% by volume of the oxidizing agent concentrate, and 2% by 10. volume of one of the chromium concentrates 7.2A to 7.2G respectively.
Zinc plated steel test panels as described in Example 7.1 were processed through each of the operating baths (Examples 7.2.1 to 7.2.14) under the conditions 15. as set forth in Example 7.1 whereafter the passi~ated panels were subjected to a silicate post~rinse treatment employing an aqueous silicate rinse solution in which the silicate concentration was varied from about 1 to about 40 g/l calculated as SiO2 at temperatures ranging 20. from 50 to 150F (10 to 66C). The panels were subsequently air dried and subjected to a neutral salt spray corrosion test as described în Example 7,l.
Similar results to those reported for Example I.l were obtained.
25.
EX~PLES 7.3.1 to 7.3.6 A series of operating baths was prepared as follows:

30.

gl. 1228~)0~) - OPERATING BATH 7.3A
Ingredient Concentration, g/l Cr2(S04)3 2.2 5- NH4HF2 .18 H2S04 1.2 22 5.3 FeNH4S4* 0.25 10. 4 7H20 1.6 *Ferrous Ammonium Su~hate= Fe(S04)-(NH4)2S04 6H20 Ingredient Concentration, g/~
15. Cr2(So4)3 5.6 --H2S04 2.7 20. ~22 5.3 4 4 0.58 Cos04-7H2o 3 75 OPERATING BATH 7.3C
25. Ingredient Concentration, g/l Cr2(S04)3 3.0 4 2 0.24 2 4 1.54 22 5.3 4S04 0.25 4S04 2.1 *Nickel Ammonium Su~phate= NiSo4-(NH4)2So4-6H2o 12~8~)00 OPERATING BATH 7.3D
_ IngredientConcentratlon, g~l 2(SO4)3 3,o 4 2 0.24 2S4 1.54 4SO4 Q.24 H22 5.3 lO. 4 H2O 1.0 OPERATING BATH7.3E
IngredientConcentration, g/l 15. 2(SO4)3 3.0 4 2 0.24 H2SO4 1.54 FeN~4'S4 0.24 20. 2 2 ;~3 H2M~o4 H20 1. O

OPERATING BATH 7. 3F

25. In~_edientConcentration, g/l Cr2(So4)3 3.0 4 2 0.24 H2SO4 1.54 30. FeNH4S4 0.24 2 2 5'3 (~H4)4(NiMoo24H6)4.4H2o 1.0 1~2~3~00 93.

Zinc plated test panels prepared as previously described in Example 1 were processed through the foregoing operating baths (Exam~les 7.3.1 to 7.3.6~
under the conditions previously described in Example 7.1 5. whereafter they were water rinsed and subjected to an aqueous silicate post~rinse treatment in a rinse solution in which the silicate concentration calculated as SiO2 was varied from about 1 to about 40 g/l at temperatures ranging from about 50 to about 150F (10 to 66C).
10. The passivated and post rinsed panels after drying were subjected to salt spray tests as described in Example 7.1 and similar results were ohtained.

Claims (116)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An aqueous acidic solution useful in the treatment of receptive metal substrates to impart a passivate film thereon comprising:
a) hydrogen ions to provide an acidic pH, b) an oxidizing agent, and c) at least one of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixture or cerium ions or mixtures thereof in an amount effective to impart increased corrosion resistance to the treated substrate.

2. An aqueous acidic solution for treating receptive metal substrates to impart a passivate film thereon comprising:
a) an acid, b) an oxidizing agent, and c) iron and cobalt ions present in an amount effective to impart increased corrosion resistance to the treated substrate.

3. An aqueous solution as claimed in claim 1, also comprising:
d) chromium ions substantially all of which are in the trivalent state.

4. An aqueous acidic solution for treating receptive metal substrates to impart a chromate passivate film thereon comprising:
a) an acid, b) an oxidizing agent, c) iron ions in combination with at least one additional metal ion selected from the group consisting of cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixture and mixtures thereof present in an amount effective to impart increased corrosion resis-tance to the treated substrate, and d) chromium ions substantially all of which are in the trivalent state.

5. An aqueous acidic solution for treating receptive metal substrates to impart a chromate passi-vate film thereon comprising:
a) an acid, b) an oxidizing agent, c) cerium ions present in an amount effective to impart increased corrosion resistance to the treated substrate, and d) chromium ions substantially all of which are in the trivalent state.

6. An aqueous acidic solution for treating receptive metal substrates to impart a chromate passi-vate film thereon comprising:
a) hydrogen ions to provide an acidic pH, b) an oxidizing agent, c) at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixture and cerium and mixtures thereof present in an amount effective to impart increased corrosion resistance to the treated substrate, d) chromium ions substantially all of which are in the trivalent state, and e) a bath soluble and compatible organic carboxylic acid present in an amount effective to impart initial hardness and clarity to the passivate film, the said organic acid having the structural formula:
(OH)a R (COOH)b wherein:
a is an integer from 0 to 6, b is an integer from 1 to 3, and R represents an alkyl, alkenyl, or aryl group containing from C1 to C6 carbon atoms;
as well as the bath soluble and compatible salts there-of.

7. An aqueous acidic solution for treating receptive metal substrates to impart a chromate passivate film thereon comprising:
a) hydrogen ions to provide an acidic pH, b) an oxidizing agent, c) at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixture and cerium and mixtures thereof present in an amount effective to impart increased corrosion resis-tance to the treated substrate, d) chromium ions substantially all of which are present in the trivalent state and present in an amount effective to produce a chromate film, and e) a bath soluble and compatible silicate compound present in an amount effective to provide improved hardness to the passivate film, and improved corrosion protection to the substrate.

8. An aqueous acidic solution for treating receptive metal substrates to impart a chromate passivate film thereon comprising:
a) hydrogen ions to provide an acidic pH, b) an oxidizing agent, c) at least one additional metal ion selected from the group consisting or iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixture and cerium and mixtures thereof present in an amount effective to impart increased corrosion resistance to the treated substrate, d) chromium ions substantially all of which are present in the trivalent state and present in an amount effective to produce a chromate film, and g) a stabilizing agent comprising a mixture of 1-hydroxy ethylidene-1,1 diphosphonic acid and citric acid as well as the bath soluble and compatible salts thereof present in an amount effective to reduce loss of the oxidizing agent and to inhibit a rise in the pH
of the solution.

9. An aqueous acidic solution as claimed in claim 1, in which ingredient A is provided by an acid.

10. An aqueous solution as claimed in claim 9, in which the said acid is a mineral acid.

11. An aqueous solution as claimed in claim 10, in which the mineral acid comprises sulphuric, nitric or hydrochloric acid or mixtures thereof.

12. An aqueous solution as claimed in claims 1, 4 or 5, having a pH of about 1.2 to about 2.5.

13. An aqueous solution as claimed in claims 1, 4 or 5, having a pH of about 1.5 to about 2.2.

14. An aqueous solution as claimed in claims 1, 4 or 5, having a pH of about 1.5 to about 2Ø

15. An aqueous solution as claimed in claims 1, 4 or 5, having a pH of about 1.6 to about 1.8.

16. An aqueous solution as claimed in claim 1, in which the said oxidizing agent, ingredient B, is present in an amount of about 1 to 20 g/l calculated on a weight equivalent effectiveness basis to hydrogen peroxide.

17. An aqueous solution as claimed in claim 16, in which the said oxidizing agent is present in an amount of about 3 to about 7 g/l calculated on a weight equi-valent effectiveness basis to hydrogen peroxide.

18. An aqueous solution as claimed in claim 1, in which the said oxidizing agent comprises a peroxide.

19. An aqueous solution as claimed in claim 18, in which the said oxidizing agent comprises hydrogen peroxide.

20. An aqueous solution as claimed in claims 6, 7 or 8, in which the said at least one additional metal ion in the said aqueous acidic solution is present in an amount up to about 10 g/l.

21. An aqueous solution as claimed in claims 6, 7 or 8, in which the said at least one additional metal ion in the said aqueous acidic solution is present in an amount of about 0.5 to about 10 g/l.

22. An aqueous solution as claimed in claim 1, in which ingredient C is present in an amount up to about 1 g/l.

23. An aqueous solution as claimed in claim 22, in which ingredient C is present in an amount of about 0.02 to about 1 g/l.

24. An aqueous solution as claimed in claim 23, in which ingredient C is present in an amount of about 0.1 to about 0.2 g/l.

25. An aqueous solution as claimed in claim 1, further containing at least one additional metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixture as well as mixtures thereof.

26. An aqueous solution as claimed in claim 25, further containing as an additional metal ion aluminium.

27. An aqueous solution as claimed in claim 26, in which the said at least one additional metal ion comprises iron.

28. An aqueous solution as claimed in claims 25, 26 or 27, in which the said at least one additional metal ion comprises cobalt.

29. An aqueous solution as claim in claims 25, 26 or 27, in which the said at least one additional metal ion comprises nickel.

30. An aqueous solution as claimed in claims 25, 26 or 27, in which the said at least one additional metal ion comprises molybdenum.

31. An aqueous solution as claimed in claims 25, 26 or 27, in which the said at least one additional metal ion comprises manganese.

32. An aqueous solution as claimed in claims 25, 26 or 27, in which the said at least one additional metal ion comprises lanthanum.

33. An aqueous solution as claimed in claims 25, 26 or 27, in which the said at least one additional metal ion comprises lanthanide mixture.

34. An aqueous solution as claimed in claims 25, 26 or 27, in which the said at least one additional metal ion comprises aluminium.

35. An aqueous solution as claimed in claims 3, 4 or 5, in which the trivalent chromium ions, ingredient D, are present in an amount of about 0.05 g/l up to saturation.

36. An aqueous solution as claimed in claims 3, 4 or 5, in which the trivalent chromium ions are pre-sent in an amount of about 0.2 to about 2 g/l.

37. An aqueous solution as claimed in claims 3, 4 or 5, in which the trivalent chromium ions are present in an amount of about 0.5 to about 1 g/l.

38. An aqueous solution as claimed in claim 1, further including halide ions.

39. An aqueous solution as claimed in claim 38, in which the said halide ions are present in an amount up to about 8 g/l.

40. An aqueous solution as claimed in claim 39, in which the said halide ions are present in an amount of about 0.1 to about 2.5 g/l.

41. An aqueous solution as claimed in claim 38, in which the said halide ions are present in an amount up to about 2 g/l.

42. An aqueous solution as claimed in claim 41, in which the said halide ions are present in an amount of about 0.1 to 0.5 g/l.

43. An aqueous solution as claimed in claim 1, further containing a surfactant.

44. An aqueous solution as claimed in claim 43, in which the said surfactant is present in an amount up to about 1 g/l.

45. An aqueous solution as claimed in claim 44, in which the said surfactant is present in an amount of about 50 to about 100 mg/l.

46. An aqueous solution as claimed in claim 1, further containing sulphate ions in an amount up to about 15 g/l.

47. An aqueous solution as claimed in claim 46, containing sulphate ions in an amount of about 0.5 to about 5 g/l.

48. An aqueous solution as claimed in claim 4, in which the said iron ions are present in an amount of about 0.05 to about 0.5 g/l.

49. An aqueous solution as claimed in claim 48, in which the said iron ions are present in an amount of about 0.1 to about 0.2 g/l.

50. An aqueous solution as claimed in claim 2, in which the said iron and the said cobalt ions are present in an amount of about 0.02 to about 1 g/l.

51. An aqueous solution as claimed in claim 50, in which the said iron and the said cobalt ions are present in an amount of about 0.1 to about 0.2 g/l.

52. An aqueous solution as claimed in claims 2, 3 or 4, further containing cerium ions present in an amount of about 0.5 to about 10 g/l.

53. An aqueous solution as claimed in claims 2, 3 or 4, further containing cerium ions present in an amount of about 1.0 to about 4 g/l.

54. An aqueous solution as claimed in claim 5, in which the said cerium ions are present in an amount of about 0.5 to about 10 g/l.

55. An aqueous solution as claimed in claim 54, in which the said cerium ions are present in an amount of about 1.0 to about 4 g/l.

56. An aqueous acidic solution as claimed in claim 1, containing cerium ions in an amount of about 0.5 to about 10 g/l.

57. An aqueous acidic solution as claimed in claim 56, in which the aqueous acidic solution contains cerium ions in an amount of about 1 to about 4 g/l.

58. An aqueous solution as claimed in claim 6, in which the said carboxylic acid, ingredient E, is present in an amount of about 0.05 to about 4 g/l.

59. An aqueous solution as claimed in claim 58, in which the said carboxylic acid is present in an amount of about 0.1 to about 1 g/l.

60. An aqueous solution as claimed in claims 6, 58 or 59, in which the said organic carboxylic acid comprises malonic, maleic, succinic, gluconic, tartaric or citric acid or mixtures thereof as well as salts thereof.

61. An aqueous solution as claimed in claims 58 or 59, in which the said carboxylic acid and salts thereof comprises succinic acid.

62. An aqueous solution as claimed in claims 58 or 59, in which the said carboxylic acid and salts thereof comprises malonic acid.

63. An aqueous solution as claimed in claims 58 or 59, in which the said carboxylic acid and salts thereof comprises maleic acid.

64. An aqueous solution as claimed in claims 58 or 59, in which the said carboxylic acid and salts thereof comprises gluconic acid.

65. An aqueous solution as claimed in claims 58 or 59, in which the said carboxylic acid and salts thereof comprises tartaric acid.

66. An aqueous solution as claimed in claims 58 or 59, in which the said carboxylic acid and salts thereof comprises citric acid.

67. An aqueous solution as claimed in claim 7, in which the said silicate compound is present in an amount of about 0.1 to about 5 g/l calculated as SiO2.

68. An aqueous solution as claimed in claim 67, in which the said silicate compound is present in an amount of about 0.1 to about 0.5 g/l calculated as SiO2.

69. An aqueous solution as claimed in claim 7, in which the said silicate compound comprises an inorganic bath soluble and compatible silicate compound present in an amount up to about 2 g/l.

70. An aqueous solution as claimed in claim 69, in which the said silicate compound comprises an alkali metal or ammonium silicate compound present in an amount up to about 2 g/l.

71. An aqueous solution as claimed in claim 7, in which the said silicate compound comprises a quaternary ammonium silicate compound present in an amount of about 0.01 to about 5 g/l calculated as SiO2.

72. An aqueous solution as claimed in claim 71, in which the said silicate compound comprises a qua-ternary ammonium silicate compound present in an amount of about 0.1 to about 0.5 g/l calculated as SiO2.

73. An aqueous solution as claimed in claims 71 or 72, in which the said silicate compound has the following structural formula:
ROR':xSiO2:yH2O
wherein:
R represents a quaternary ammonium radical substituted with four organic radicals selected from the group consisting of alkyl, alkylene, alkanol, aryl, or alkylaryl radicals, or mixtures thereof;

R' represents R or a hydrogen atom;
x is an integer from 1 to 3, and y is an integer from 0 to 15.

74. An aqueous acidic solution as claimed in claim 1, further containing a bath soluble compatible organic carboxylic acid or a compatible salt thereof.

75. An aqueous solution as claimed in claim 74, in which the bath soluble and compatible organic carboxylic acid is present in an amount effective to impart initial hardness and clarity to the passivate film, the organic acid having the structural formula:
(OH)a R (COOH)b wherein:
a is an integer from 0 to 6;
b is an integer from 1 to 3; and R represents an alkyl, alkenyl, or aryl group containing from C1 to C6 carbon atoms;
as well as the bath soluble and compatible salts thereof.

76. An aqueous solution as claimed in claim 75, in which the said carboxylic acid is present in an amount of about 0.05 to about 4 g/l.

77. An aqueous solution as claimed in claim 76, in which the said carboxylic acid is present in an amount of about 0.1 to about 1 g/l.

78. An aqueous solution as claimed in claims 75, 76 or 77, in which the said organic carboxylic acid comprises malonic, maleic, succinic, gluconic, tartaric, or citric acid or a mixture thereof as well as salts thereof.

79. An aqueous solution as claimed in claim 8, in which the said 1-hydroxy ethylidene-1,1 diphosphonic acid, ingredient G, is present in an amount of about 0.05 to about 3 g/l.

80. An aqueous solution as claimed in claim 79, in which the said 1-hydroxy ethylidene-1,1 diphosphonic acid is present in an amount of about 0.1 to about 0.5 g/l.

81. An aqueous solution as claimed in claim 8, in which the said citric acid is present in an amount of about 0.1 to about 10 g/l.

82. An aqueous solution as claimed in claim 81, in which the said citric acid is present in an amount of about 0.5 to about 1.5 g/l.

83. An aqueous concentrate suitable for dilution with water and by addition of:
a) hydrogen ions to provide an acidic pH, b) an oxidizing agent, and c) at least one metal ion selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixture and cerium, and mixtures thereof to produce an operating bath suitable for treating a receptive metal substrate to impart a chromate passivate film thereon, the said concentrate comprising about 10 to about 80 g/l of chromium ions substantially all of which are present in the trivalent state and about 5 to about 50 g/l calculated as SiO2 of an organic quaternary ammonium silicate.

84. An aqueous concentrate as claimed in claim 83, further including up to about 50 g/l of halide ions.

85. An aqueous concentrate as claimed in claims 83 or 84, further including a surfactant present in an amount of up to about 5 g/l.

86. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 4, at a tempera-ture of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon.

87. A receptive substrate whenever provided with a passivate by a process as claimed in claim 86.

88. A process for treating a receptive metal substrate to impart a passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 2, at a temperature of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon.

89. A receptive substrate whenever provided with a passivate by a process as claimed in claim 88.

90. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 5, at a temperature of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon.

91. A receptive substrate whenever provided with a passivate by a process as claimed in claim 90.

92. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 6, at a temperature of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon.

93. A receptive substrate whenever provided with a passivate by a process as claimed in claim 92.

94. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 7, at a temperature of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon.

95. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 7, at a temperature of about 40° to about 150°F(4° to 66°C) for a period of time sufficient to form a passivate film thereon, contacting the passivated substrate with a dilute aqueous rinse solution for a period of at least about one second containing a bath soluble and compatible sili-cate compound present in an amount effective to impart improved corrosion resistance and hardness to the passivate film, and thereafter drying the passivated silicate rinsed substrate.

96. A receptive substrate whenever provided with a passivate by a process as claimed in claims 94 or 95.

97. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 8, at a temperature of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon.

98. A process for treating a receptive metal substrate to impart a chromate passivate film thereon which comprises the steps of contacting the substrate with a solution as claimed in claim 8, at a temperature of about 40° to about 150°F (4° to 66°C) for a period of time sufficient to form a passivate film thereon, contacting the passivated substrate with a dilute aqueous rinse solution for a period of at least about one second containing a bath soluble and compatible silicate compound present in an amount effective to impart improved corrosion resistance and hardness to the passivate film, and thereafter drying the passi-vated silicate rinsed substrate.

99. A receptive substrate whenever provided with a passivate by a process as claimed in claims 97 or 98.

100. A process for treating a receptive metal substrate to impart an improved chromate passivate film thereon which comprises the steps of providing an aqueous acidic solution containing effective amount of chromium ions substantially all of which are in the trivalent state, hydrogen ions to provide a pH of about 1.2 to about 2.5, an oxidizing agent, and at least one of iron, cobalt, nickel, molybdenum, manganese, alumi-nium, lanthanum, lanthanide mixtures and cerium as well as mixtures thereof, contacting the substrate with the said aqueous acidic solution for a period of time sufficient to form a passivate film thereon, contac-ting for a period of at least about one second the passivated substrate with a dilute aqueous rinse solu-tion containing a bath soluble and compatible silicate compound present in an amount effective to impart im-proved hardness to the passivate film and improved corrosion resistance to the substrate and thereafter drying the passivated silicate rinsed substrate.

101. A process as claimed in claim 100. further including the step of water rinsing the said passivated substrate prior to contracting the passivated substrate with the said aqueous silicate rinse solution.

102. A process as claimed in claim 100, in which the said aqueous rinse solution contains from about 1 to 40 g/l of the said silicate compound calculated as SiO2.

103. A process as claimed in claim 102, in which the said aqueous rinse solution contains from about 5 to about 15 g/l of the said silicate compound cal-culated as SiO2.

104. A process as claimed in claim 100, in which the said silicate compound comprises an inorganic compound.

105. A process as claimed in claim 104, in which the said inorganic silicate compound comprises an alkali metal or ammonium silicate.

106. A process as claimed in claim 100, in which the said silicate compound comprises an organic silicate compound.

107. A process as claimed in claim 106, in which the said organic silicate compound comprises a quaternary ammonium silicate compound.

108. A process as claimed in claim 106, in which the said organic silicate compound has the structural formula:
ROR':xSiO2:yH2O
wherein:
R represents a quaternary ammonium radical substituted with four organic radicals selected from the group consisting of alkyl, alkylene, alkanol, aryl, alkylaryl radicals or mixtures thereof;
R' represents a hydrogen atom;
x is an integer from 1 to 3; and y is an integer from 0 to 15.

109. A process as claimed in claim 100, in which the said aqueous rinse solution is at a temperature of about 50° to about 150°F (10° to 66°C).

110. A process as claimed in claim 100, in which the step of contacting the passivated substrate with the said aqueous rinse solution is carried out for a period of at least about one second up to about one minute.

111. A process as claimed in claims 100 or 101, in which the said rinse solution further contains from about 0.05 to about 5 g/l of a compatible wetting agent.

112. A process as claimed in claims 100 or 101, in which the said rinse solution further contains from about 1 to about 50 g/l of an emulsifiable oil.

113. A process as claimed in claims 100 or 101, in which the said rinse solution further contains an alkali metal or ammonium nitrite or mixtures thereof in an amount of about 0.1 to about 1 g/1.

114. A receptive substrate whenever subjected to a process as claimed in claim 100.

115. A receptive substrate as claimed in claims 87, 89 or 91, in which the surface treated comprises zinc, zinc alloy, cadmium, cadmium alloy, aluminium, aluminium alloy, magnesium or magnesium alloy.

116. A receptive substrate as claimed in claims 93 or 114, in which the surface treated comprises zinc, zinc alloy, cadmium, cadmium alloy, aluminium, alumi-nium alloy, magnesium or magnesium alloy.