AU605301B2 - Process for phosphating metal surfaces - Google Patents

Description

<4 Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Application Number: Lodged: Int. Class Complete Specification Lodged: S S S Ace ed 6 Daiority:

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*6 Related Art: 4•49** Published: S *S marof Applicant: 00 Address of Applicant: ActuallInventor: 0 0 Address for Service: NIPPON PAINT COMPANY, LTD.

2-1-2, Oyodokita, Oyodo-ku, Osaka-shi, Osaka-fu, JAPAN YASUTAKE MINO, RYOICHI MURAKAMI and KOICHI SAITO EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

Complete Specification fc r the invention entitled: This document contains the or the invention entitled: amendments made under amendments made under PROCESS FOR PHOSPHATING METAL SURFACES Section 49 and is correct for printing The following statement is a full description of this invention, including the best method of performing it known to la BACKGROUND OF THE INVENTION The patent application is a Patent of Addition application to Australian Patent No. 554406 (81507/82) to the same Applicant.

Nippon Paint Co. Ltd., of Osaka, Japan recently filed Japanese Patent Publications (unexamined) No. 107784/1980 and No. 152183/1980 on phosphating methods of treating iron-based metal surfaces which are particularly suitable for treating manufactured products having complicated surfaces, such as automobile bodies. The above phosphating methods are in use commercially in the automotive industry for pretreating automobile bodies prior to cationic electrocoating, which are the coating processes now used extensively in this industry. The phosphating method of Japanese Patent Publication No. 107784/1980 is carried out by first subjecting the metal surface to a dipping treatment with an acidic aqueous solution containing to 1.5 g/l of zinc ion, 5 to 30 g/1 of phosphate ion, and 0.01 to 0.2 g/l of nitrite ion and/or 0.05 to 2 g/l of m-nitrobenzene-sulfonate ion at a bath temperature of 400 to 700 for 15 seconds or more, followed by spraying with the above solution for 2 seconds or more. The other method, S i.e. the method of Japanese Patent Publication No. 152183/80, comprises spraying onto the metal surface an S acidic aqueous solution containing 0.4 to 1.0 g/l of zinc ion, 5 to 40 g/l of phosphate ion, 0.01 to 0.2 g/l of nitrite ion and 2.0 to 5.0 g/l of chlorate ion at 40° to Ss 70 0 C for 40 seconds or more.

Recently, in automotive industry, consistent with the aim of further improving corrosion resistance after the 1 I ~i application of.a siccative coating, steel components which are plated on one surface only with zinc or a zinc alloy have come to be used as materials for automobile bodies.

When the processes of the above Japanese Patent Publications are applied to such materials to metal components having both iron-based metal surfaces and zinc-based metal surfaces), the iron-based surfaces are provided with a phophate coating film having a low film thickness with uniform and dense cubic or plate-like crystals, as well as 10 excellent adhesion and corrosion-resistance. Such phosphate S. S coating on the iron-based surface is suitable as a substrate for cationic electrocoating. However, in the case of the phosphate coating film formed on the zinc-based surfaces, the resistance to salt water spraying after the application 15 of a cationic electrocoating thereto is insufficient, and secondary adhesion (by immersion test of the film with cross-hatched scratches in warm water) after cationic 0. S• electrocoating intermediate coating top coating is greatly inferior to that on the iron-based surfaces. In 20 addition to the above Japanese Patent Publications, the following references disclose phosphating compositions for metal surfaces: U.S. 3,338,755 issued August 29, 1967 to Jenkins et al.

This patent discloses a process for phosphating metal surfaces with a phosphating solution containing zinc, manganese, phosphate, nitrate, and nitrite, as essential ingredients, in stated proportions.

U.K. 983,924 issued February 24, 1965 to Pyrene Co., Ltd. is by the same inventors as U.S. 3,338,755 and has the 2 same general disclosure.

German 29 31 693, issued December 11,- 1980 to Fosfa-Col, discloses a phosphating process using a solution containing zinc, manganese, phosphate, nitrate, and chlorate ions in stated gram-atom relationships.

However, none of the above proposed phosphating methods have succeeded in giving satisfactory results with the above combination of substrate materials.

Japanese Patent J50139-039 (JA 197511) discloses a conversion coating solution containing manganese ions for the treatment of zinc surfaces. However, this prior art solution contains from 3 to 20 g/l of zinc ions, which will result in a conversion coating having leaf-like crystals on iron-based surfaces. Such leaf-like crystals are unsuitable as a substrate for cationic electrocoating. Hence, the solutions.of this patent are unsuitable for treating both zinc-based and iron-based surfaces.

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SDETAILED DESCRIPTION OF THE INVENTION The present inventors have now surprisingly found that 20 by the inclusion of defined quantities of manganese ion in certain acidic aqueous phosphating solutions, very satisfactory results can be attained with these materials, and that /,yi such aqueous solutions containing zinc ion, phosphate ion, manganese ion and a conversion coating accelerator can be applied either by dipping, spraying, or a combination thereof. The inventors have further found that while chlorate ion can be present as well, it is not an essential 3 U-i~m;L~Y~IPI' 4 component of the treating solution for spray applications, provided the defined amounts of manganese ion are present therein, and that even when chlorate ion is added in a preferred embodiment, the amounts of said ion can be markedly decreased as compared with those of heretofore known compositions.

Accordingly, the present invention relates to a treating method for forming phosphate coatings on metal surfaces. More particularly, it relates to a treating method for surfaces of a metal such as a car body which have both iron-based surfaces and zinc-based surfaces, and to aqueous treating compositions, concentrates useful in their preparation, and to the phosphate coating films resulting from their use. The treating method of the invention is especially designed for forming phosphate coating films suitable for electrocoating, particularly cationic electrocoating.

The process of the invention is carried out by contacting the metal surface(s) to be phosphated with an acidic aqueous solution containing: from about 0.5 to 1.5 g/l, preferably 0.7 to 1.2 g/l of zinc ion; from 0.6 to 3 g/l preferably 0.8 to 2 g/l of manganese ion; and a conversion coating accelerator, wherein said contacting is carried out by spraying the metal surface with the solution.

The conversion coating accelerator is preferably at least one of the following: i) from 0.01 to 0.02 g/l, preferably 0.04 to 0.15 g/l, of nitrite ion; ii) from 0.05 to 2 g/l, preferably 0.1 to 1.5 g/l, of m-nitrobenzene-sulfonate ion; and iii) from 0.5 to 5 g/l, preferably 1 to 4 g/l, of hydrogen peroxide (based on 100% H 202).

The metal surface(s) is contacted with the acidic aqueous solution of the invention by spraying the solution onto the surface of the metal. This may advantageously be followed by dipping the metal surface into the solution.

Optionally, the above acidic aqueous solution may also contain one or more of the following: from 0.1 to 4 g/l, preferably 0.3 to 2 g/l, of nickel ion; from 1 to 10 g/l, preferably 2 to 8 g/l, of nitrate ion; and from 0.05 to 3 g/l, preferably 0.5 to 1.9 g/l, of chlorate ion for both dipping and spraying use. However, where a spray process is used with a zinc ion concentration of more 1 g/l, i.e. from more than 1.0 to 2.0 g/l of zinc *ion, then up to 5 g/l of chlorate ion, e.g.

from 2 g/l to 5 g/l, can be present in the solution. Use of chlorate concentrations in excess of these ranges is not advisable since at higher chlorate levels the phosphating rate *CO becomes too rapid for satisfactory control.

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The above process is preferably carried out at a temperature of from about 400 to about 70 0 C, preferably about 450 to about 60 0 C, for a contact time of at least S seconds, preferably at least 15 seconds, and more preferably about 30 to about 180 seconds, and most preferably about to about 120 seconds, as hereinafter discussed. The period

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of treatment is generally at least about 15 seconds for dipping and at least about 5 seconds for spraying. It should be noted that at temperatures below about 40 0

C,

coatings can be formed; however the coating is sparse, coating formation is relatively slow and longer times are required to form satisfactory coatings. At temperatures above 7 0 0, the conversion coating accelerators begin to decompose at an unacceptable rate, changing the composition of the solution and resulting in an unacceptable conversion coating. Also, precipitates begin to form in the bath.

6 Following the above treatment, the phosphated metal surface(s) are then coated with a siccative coating by a known electrocoating process, preferably by the cationic electrocoating process.

The term "metal surface(s)" as used herein is understood to mean iron-based surfaces, iron alloy-based surfaces, zinc-based surfaces, and zinc alloy-based surfaces. Zinc-based and zinc alloy-based surfaces include for example, zinc plated steel plate formed by hot dipping, alloyed zinc plated steel plate formed by hot dipping, zinc 0* *o

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plated stucel piate formed by cl(-ctroplati ng, alloyed zinc plated steel plate formed by electroplating, etc.

Additionally, an important advantage of the present invention is that surfaces of metal components such as car bodies that contain both iron-based surfaces and zinc-based surfaces, can be treated by the process of the invention with excellent results. In fact, the process of the invention produces better conversion coatings than are obtainable with conventional dip or spray treating processes, and the amount of etching of the metal surfaces during the present process is only 2/3 to 4/5 that of conventional processes, o o Sso that both the quantity of chemicals used in the process as well as sludge formation is only from 2/3 to 4/5 that of conventional processes. Needless to say, however, the proc cess of the present invention is not limited to the treatment of metal components having both iron-based and o zinc-based surfaces, the present process is equally applicable to the treatment of a single metal surface of a o* type described above.

The metal surface to be phosphated is first degreased by dipping in and/or spraying with a known alkaline degreasing agent at 50° to 60 0 C for a few minutes; washed with tap water; dipped in and/or sprayed with a known surface conditioner at room temperature for 10 to 30 seconds; and the thus treated metal surface is then contacted, according to the present process, with an acidic aqueous solution of the invention at about 400 to about 70 0 C for at least 5 seconds. Finally, the thus treated metal surface is -7- I I I S. 0 0O 00 0S SO 0 0

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washed with tzip water and then with deionized water. Also, an acidic final chromate rinse can be employed before the rinse with deionized water.

In a preferred embodiment of the invention, use is made of a dipping procedure. In this enbodinent, the acidic aqueous solution preferably contains (a from about 0.5 to about 1.5 g/l, more preferably about 0.7 to about 1.2 g/l, of zinc ion; (b from about 5 to about 30 g/l, more preferably 10 about 10 to about 20 g/l, of phosphate ion; (c from about 0.6 to about 3 g/l, more preferably about 0.8 to about 2 g/l, of manganese ion; and (d the aforesaid conversion coating accelerator(s) in the quantities given above.

While these ranges are preferred, they can"be adjusted within th&" broader limits stated above depending on the intended objects, materials and conditions used, However, certain general criteria for this dip process are useful here as follows: When the amount of zinc ion is less than about 0.5 g/l, an even phosphate film is usually not formed on an iron-based surface, and a partially blue-colored film is often formed. When the amount of zinc ion exceeds about g/l, then though an even phosphate film is formed, the film formed on an iron-based surface tends to be in the form of 25 leaf-like crystals, which are unsuitable as a substrate for cationic electrocoating. IhThen the amount of phosphate ion in the solution is less than about 5 g/l, an uneven film results. Wien the amount of phosphate ion exceeds about g/l, no further improvement in the phosphate film is 4~7 8 P~iC~; ~ia-Lx- II:I '4.

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*5* 0@ realized and hence, while not harmful, use of phosphate ion above about 30 g/1 is uneconomical. When the amount of manganese ion is less than about 0.6 g/l, the manganese content in the film formed on the zinc-based surface is insufficient, resulting in inadequate adhesivity of the coating film to the phosphate substrate after cationic electrocoating. When the amount of manganese ion exceeds about 3 g/l, no further improvemnent in the phosphate coating is realized, and hence, it is uneconomical to use amounts in excess of about 3 g/1.

With respect to the conversion coating accelerator(s) used in the solutions of the invention, when the amount of these accelerators is less than the lower amounts given above, the conversion coating on iron-based surfaces is inadequate, forming yellow rust, etc. When the amount of accelerator exceeds the higher amounts given above, a blue-colored uneven film is formed on iron-based surfaces.

In another preferred embodiment of the invention, use is made of a spraying procedure. In this embodiment, the acidic aqueous solution of the invenEion can contain from about 0.1 to about 2.0 g/1, preferably about to about 1.5 g/l and more preferably about 0.; to about 1.2 g/1, of zinc ion; from about 5 to about 30 g/l, preferably about to about 20 g/1, of phosphate ion; from about 0.2 to about 3 g/1, and preferably about 0.6 to about 3 g/l, of manganese ion; and the aforesaid conversion coating accelerator(s) i the quantities given above.

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cc c cc c ee e Here again, the above ranges can be adjusted depending on the intended objects, materials and conditions used.

However, when the amount of zinc ion is less than 0.1 g/l, a even phosphate film will seldom form on an iron-based surface, and a partially blue-colored film is formed. On the other hand, when the amount of zinc ion is in excess of g/l, then the film tends to be in the form of leaf-like crystals and deficient in secondary adhesion, which renders it unsuitable as a substrate for cationic electrocoating.

When the amount of phosphate ion in the solution is less than about 5 g/l, an uneven film results, whereas when the anount of phosphate ion exceeds 30 g/1, no further improvement in the phosphate film is realized and hence, the use of greater quantities of phosphate is uneconomical. When the amount of manganese ion is less than about 0.2 g/l, the manganese content in the film formed on the zinc-based surface is insufficient, resulting in inadequate adhesivity of the siccative coating film to the phosphate conversion coating after cationic electrocoating. When the amount of manganese ion exceeds 3 g/l, no further improvement in the phosphate coating is realized and hence, excess use thereof is uneconomical. Furthermore, spot rusting of iron-based surfaces will increase. With respect to the quantities of conversion coating accelerator(s), very similar results to those stated above in connection with the solution for dipping use are obtained.

In addition to the dipping and spray applications described above, certain coirniercial conditions may warrant 1

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10 contacting the metal surface with the coating solution in a combination of different methods, such as by intermittent spraying of the metal surface, by spraying followed by dipping, or by dipping followed by spraying. The coating composition can be applied by these methods without a loss in coating formation.

For example, the coating solution can be applied by intermittent spray, where the metal substrate is sprayed for about 5 to about seconds, then allowed to stand without any coating application for about 5 to about 30 seconds, and then sprayed for at least 5 seconds with a total spray time of at least seconds. This cycle can be carried out once, twice or three times.

S..Furthermore, in treating metal components having complicated surface profiles, such as with car bodies, the S* 15 components can be subjected first to dipping treatments for about 15 seconds or more, preferably about 30 to about 90 seconds, and then to spray treatment with the solution about 2 seconds or more, preferably about 5 to about 45 seconds, in order to wash out the sludge Thich adheres during dipping, the spray treatment se 20 is preferably carried out for as long a period within the above range as the speed of the production line will permit. Dipping application is preferred over spray application, with a duooubgspray application being most preferred. Alternatively, the coating can be applied by first spraying the metal surface for from about 2 to 15 seconds, and then dipping the metal surface into the coating solution for at least about; 15 seconds, preferably from about 90 to about 120 seconds. This method of applying the coating composition helps to eliminate "hash" marks on the metal surface as the metal surface enters the dip coating solution. The "hash" marks result when the conveyor system fails 11 to move the substrate at a constant velocity, or when the substrate "sways" in a direction perpendicular to the direction of conveyor movement.

Of course, the above treating times and treating sequences can be changed according to the composition of the metal substrate to be treated and the treating solution and conditions to be used.

For spray applications, the coating solution is conventiently applied at a spraying pressure of from about 0.5 to about 2 Kg/cm 2 Irrespective of the application means and the contacting solution used, theresulting phosphate film present on the zincbased surface should preferably contain from about 1.0 to about 20o by weight, more preferably from about 2 to about 18% by *2 2 b15 weight, and most preferably from about 5 to about 18% by weight of manganese ion, which is very important for the subsequent cationic electrocoating. The zinc ion is present in from about 28 to about 45% by weight, preferably about 28 to about 40% by weight. When nickel ion is used in the solution, then from about *20 0.3 to about 4% by weight, preferably about 0.5 to about 4% by weight of nickel is present in the coating. The remainder of the coating is phosphate and water, except for qu,-ntities of other ;ions such as sodium, calcium, magnesium, etc. that total less than 1% by weight. It has also been found that as the content of manganese in the bath increases, increased manganese content i4 in the coating results. However, increasing the manganese level of the coatings above the ranges given above does not improve coating quality.

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As an example of a source of zinc ions for use in the practice of the invention, one or more of the following can be employed: zinc oxide, zinc carbonate, and zinc nitrate.

As an example of a source of phosphate ions, one or more of the following can be used: sodium phosphate, zinc phosphate, and manganese phosphate. As an example of a source of manganese ions, one or more of the following can be employed: manganese carbonate, manganese nitrate, manganese chloride, and manganese phosphate. As an example of sources of conversion coating accelerators, sodium nitrite, ammonium nitrite, sodium m-nitrobenzene sulfonate, and hydrogen peroxide can be employed herein. With respect to the optional ingredients that can be added to the acidic aqueous solution of the invention, the addition of nickel ion to a manganese-containing composition results in further improvement in the performance of the phosphate conversion coating, so that the adhesion and the corrosion-resistance of the film produced by cationic electrocoating are also further improved.

As sources of the optional ingredients, nickel carbonate, nickel nitrate, nickel chloride, nickel phosphate etc. are used for nickel ions; sodium nitrate, ammonium nitrate, zinc nitrate, manganese nitrate, nickel nitrate,

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13 etc. for nitrate ions, and chloric acid, sodium chlorate, ammonium chlorate, etc. for chlorate ions.

The acidic aqueous treating solutions are conveniently prepared by diluting an aqueous concentrate which contains a number of the solution ingredients in proper weight ratios, and then addirg other ingredients as needed to prepare the treating solutions of the invention. The concentrates are advantageously formulated to contain zinc ion, in a weight proportion of 0.1 to 2:5 to 30 0.2 to 3 0.1 to 4. The concentrates are preferably formulated to contain at least about 25 g/l and more preferably from about 50 g/l to about 130 g/l, of zinc ion.

The invention will be better understood from the following examples, which are given to illustrate the invention and 15 not to limit it.

S0 0 0 S S 14 tw EXAMPLES I XIV Examples I through IX are examples of the process and compositions of the invention. Examples X through XIV are examples using known compositions, given for comparison purposes. The treating process used, which is common to all of EXAMPLES I XIV, is given below, with the aqueous coating compositions of each example set forth in Table I, while the metal treated and the test results obtained 'following the phosphate treatment are given in Table 2.

of all four metal surfaces given in Table 2 1 0 were treated simultaneously according to the following procedure: Gibe* degreasing, using an alkaline degreasing agent (Nippon Paint Co., "RIDOLINE SD200", 2% by weight) which was sprayed on the metal surfaces at 60 0

C

15 for 1 minute, followed by dipping in the solution for 2 minutes; i•o. the metal surfaces were then washed with tap water at room temperature for 15 seconds; the metal surfaces were next dipped into a surface 0 se o 20 conditioner (Nippon Paint Co., "FIXODINE 5N5", 0.1% by weight) at room temperature for 15 seconds; the metal surfaces were then dipped into an acidic aqueous solution given in Table 1 at 52'C for 120 seconds; the metal surfaces were washed with tap water at room temperature for 15 seconds; the metal surfaces were then dipped into deionized water at room temperature for 15 seconds; II i the surfaces were then dried in hot air at 100 0

C

for 10 minutes. At this stage the appearance and film weight of the treated metal surfaces was determined,'with the results set forth in Table 2; a cationic electrocoating material (Nippon Paint Co., "Power Top 30 Dark Gray") was coated to 20 i thickness onto the treated metal surfaces (voltage 180 treatment time 3 minutes), followed by baking at 180 0 C for 30 minutes. One sample of each electrocoated plate so obtained was sub-

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jected to the brine spray test.

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SA second sample of each electrocoated plate so obtained o was coated with an intermediate coating material (Nippon S. Paint Co., "ORGA T0778 Gray") to 30 p thickness, followed by baking at 140 0 C for 20 minutes, and a top coating material (Nippon Paint Co., "ORGA T0626 Margaret White") in 40 i eg. thickness was then applied, followed by baking as above. Accordingly, coated plates with a total of 3 coatings and 3 bak-

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ings were obtained. The coated plates were subjected to the adhesion test, and with the cold rolled steel plate, to the spot rusting test.

The testing procedures referred to above are described below: S 4 Brine spraying test (JIS-Z-2871): Cross-cuts were made on an electrocoated plate; brine was sprayed thereon for 500 hrs (zinc plated steel plate) or 1000 hrs (cold rolled steel plate).

Adhesion test: -16- VW.. 6 6 0066

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After dipping a coated plate in deionized water at for 10 days, grids (100 squares) were made at 1 mm intervals or at 2 mm intervals using a sharp cutter; an adhesive tape was attached to each surface; and the number of squares of coating film that remained on the plate after the removal of the adhesive tape were counted.

Spot rusting Lest: A coated plate was set at a 15 degree angle to the horizontal plane, and an arrow with a cone shaped head with a 10 90 degree vertical angle, made of alloyed steel (material quality, JIS-G-4404, hardness Hv 700 or higher) weighing 1.00 g and 14.0 mm in total length was dropped repeatedly from a distance of 150 cm, until 25 scratches were-made on'the S coated surface. Subsequently, the coated plate was subjected to 4 cycles of testing, each cycle consisting of first the 4 brine spray test (JIS-Z-2871, 24 hrs), second, a moisture test (temperature of 40 0 C, relative humidity 85%, 120 hrs), and third, standing at room temperature (24 hrs). Test results are shown in Table 2.

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Table 1 5.4 S .e 5 S.

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S S Sn~ S 1 Composition of Acidic Aqueous Ex.I Ex.II EX.III Ex.IV EX.V EX.VI EX.VII EX.VIII EX.IX EX.X EX.XI EX.XII EX.XIII EX.XIV solution, points Zn 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.7 1.2 0.69 0.8 1.0 1.0

PO

4 14.0 14.0 14.0 14.0 14.0 14.0 14.0 10.0 20.0 11.40 14.0 14.0 14.0 20.0 Hn 0.8 2.0 2.0 0.8 0.8 2.0 0.8 0.8 0.8 0.5 0.3 0.8 Ni 2.0 0.3 2.0 0.3 0.3 0.3 0.3 0.38 0.5 0.3 0.3

NO

2 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.07 0.08 0.06 0.06 0.06 112 02 1.0 NO 3 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 1.6 3.0 4.0 4.0 CIO 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 1.49 0.5 0.7 0.7 0.7

BF

4 0.8 Fe(III) 0.018 Total Acidity kpoint) 17.5 19 19 18 20 19.5 18 18 24 14.5 17 17 17 26 Acidity of Free Acid 0.9 0.09 0.9 0.9 0.9 0.9 0.9 0.7 1.0 0.8 0.9 0.9 0.9 1 point

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000 0 0 0 TABLE 2 Metal Test Item EX.I EX.II EX.I1l EX.IV EX.V EX.VI IEX.VlI Hot Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness dipped 2 density density density density density density density zinc Film weight(g/m )3.2 2.8 2.6 3.0 3.1 2.7 3.2 alloy Brine spray plated Cay, in mm) 2.5 2.0 1.5 1.5 1.5 1.5 on Adhesivity steel 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 plate 1 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated 2 density density density density density density density zinc on Film weight(g/m )2.5 2.0 2.4 2.2 2.4 2.4 2.1 steel Brine spray plate (av. in mm) 3.5 3.0 2.0 2.5 2.0 2.0 Adhes iv ity 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 1 mm cuts 80/100 90/100 100/100 95/100 100/100 100/100 100/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated 2 density density density density density density density zinc Film welght~g/m )3.2 2.9 2.6 3.1 3.2 2.8 alloy Brine spray on (av. in mm) 2.0 2.0 1.5 2.0 1.5 1.5 steel Adhesivity plate 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 1 mm cuts 100/100 100/100 100/100 1 100/100 100/100 100/100 100/100 Cold Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness rolled 2 density density density density density &density density steel Film weight(g/m )2.5 2.2 2.2 2.3 2.2 2.0 2.2 plate Brine spray (av, in mm) 1.5 1 greater than11>11 Adhesivity 1 11 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 1 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 Spot rusting (ave. in mm) 0.96 1.00 1 0.88 1 0.98 0.91 1 0.96 1 0.97 S 0e* S S S

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S SS SeS S S. S S S S S* S S S S 5 550 .5S S S 555 TABLE 2 (continued) Metal Test Item EX.Vil EX.IX EX.X EX.Xl EX.Xil IEX.XIll EX.XV Hot Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness dipped 2 density density density zinc Film weight(g/m 2 2.9 2.7 4.5 4.5 4,0 4.2 4.6 alloy Brine spray plated (av in mm) 1.5 1%5 5.5 3.5 4.0 3.5 on Adhesivity steel 2 mm cuts 100/100 100/100 35/100 58/100 68/100 52/100 0/100 pi.te 1 mm cuts 100/100 100/100 0/100 0/100 0/100 0/100 0/100 Elac-fro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated 2 density density density zinc on Film woight(g/m 2 2.3 2.3 3.7 3.5 3.3 3.5 3.8 steel Brine spray plate d(av in mm) 2.5 2.5 10.5 6.5 6.0 7.0 Adhesivity 2 mm cuts 100/100 100/100 0/100 24/100 33/100 25/100 0/100 I mm cuts 100/100 95/100 0/100 0/100 0/100 0/100 0/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated 2 density density density zinc Film weight(g/m 2 3.0 2.9 4.3 4.0 3.6 3.8 alloy Brine spray on (av, in mm) 2.0 2.0 5.0 3.0 3.0 3.5 steel Adhesivity plate 2 mm cuts 100/100 100/100 20/100 64/100 52/100 48/100 0/100 I mm cuts 100/100 100/100 0/100 3/100 12/100 6/100 0/100 Cold Film appearance good evenness good evenness blue coloured good evenness good evenness good evenness good evenness rolled density density uneven density density density steel Film weight(g/m 2 2.2 2.0 0.8 3.1 2.9 3.0 3.4 plate Brine spray (av, in mm) 1 1 4 1.5 1.5 1.5 Adhesivity 2 mm cuts 100/100 100/100 100/100 100/100 1, 10 100/100 0/100 1 mm cuts 100/100 100/100 80/100 100/100 I 100/100 0/100 Spot rusting (ave. in mm) 0.96 0.98 3.10 1.10 1.30 1.30 2.52 In Table 2 above, brine spray and spot rusting each indicate average value (mm) of the laroest diameter of blisters and rust spots, respectively.

EXAMPLES XV XXXI EYAMPLES XV through XXV are examples of the process and compositions of the invention. EXAMPLES XXVI through XXXI are examples using known compositions, given for comparison purposes.

The treating process used, which is common to all of EXAMPLES XV XXXI, is given below, with the aqueous coating composition of each example set forth in Table 3, while g the metal treated and the test results obtained following the phosphate treatment are 'given in Table 4.

Samples of all four metal surfaces given in Table 4 were treated simultaneously according to the following procedure: degre sing, using an alkaline degreasing agent (Nippon Paint Co., "RIDOLINE S102", 2% by weight) which was sprayed on the metal surfaces at 60 0

C

for 2 minutes; 20 the metal surfaces were then washed with tap water at room temperature for 15 seconds; the metal surfaces were then sprayed with an acidic S aqueous solution given in Table 3 at 52 0 C for 120 seconds, (in EX. XXVI, first sprayed for 15-seconds discontinued spraying for 15 seconds, and again sprayed for 105 seconds) spraying pressure -0.8 Eg/ cm 2 (gauge pressure); the metal surfaces were washed with tap water at room temperature for 15 seconds; 21i -1X~

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the metal surfaces were then dipped into deionized water at room temperature for 15 seconds; the surfaces were then dried in hot air at 100 0

C

for 10 minutes. At this stage the appearance and film weight of the treated metal surfaces was determined, with the results set forth in Table 4; a cationic electrocoating material (Nippon Paint Co., "Power Top U-30 Dark Gray") was coated to 20 v thickness onto the treated metal surfaces (voltage 180 treatment time 3 minutes), followed by baking at 180°C for 30 minutes. One sample of each electrocoated plate so obtained was subjected to the brine spray test.

o* A second sample of each electrocoated plate so obtained o 15 was coated with an intermediate coating material (Nippon Paint Co., "ORGA T0778 Gray") to 30 p thickness, followed by baking'at 140 0 C for 20 minutes, and a top coating mater- .ial (Nippon Paint Co., "ORGA T0626 Margaret White") in 40 v thickness was then applied, followed by baking as above.

20 Accordingly, coated plates with a total of 3 coatings and 3 bakings were obtained. The coated plates were subjected to the adhesion test, and with the cold rolled steel plate, to the spot rusting test.

The testing procedures referred to above are described below: Brine spraying test (JIS- Z-2871): Cross-cuts were made on an electrocoated plate; 5% brine was sprayed thereon for 500 hrs (zinc plated steel plate) or 1000 hrs (cold rolled steel plate).

I

22 'i 1 Adhesion test: After dipping a coated plate in deionized water at for 10 days, grids (100 squares) were made at 1 mm intervals or at 2 mm intervals using a sharp cutter; an adhesive tape was attached to each surface; and the number of sauares of coating film that remained on the plate after the removal of the adhesive tape were counted.

Spot rusting test: A coated plate was set at a 15 degree angle to the horiz- 10 ontal plane, and an arrow with a cone shaped head with a S degree vertical angle, made of alloyed steel (material JIS- G-4404, hardness Hv 700 or higher) weighing 1.00 g and 14.0 mm total length wcr dropped repeatedly from a distance of 150 cm, until 25 scratdhes were made on the coated surface. Subsequently 15 the coated plate was subjected to 4 cycles of testing, each cycle consisting of first the brine spray test (JIS-Z-2871, 24 hrs), second a moisture test (temperature of 40°C, relative humidity 85%, 120 hrs), and third, standing at room temperature (24 hrs). After testing, the average value (mm) of S 20 the largest diameter of rust spots and blisters was obtained, with the results shown in Table 4.

Determination of Mn in coating.

A phosphated plate was dipped in a 5% aqueous chromic acid solution (75 0 C) for 5 minutes and the weight of the conversion coating was calculated from the weight difference of the plate before and after said treatment. Next, the amount of manganese dissolved out and contained in the said aqueous 23 chromic acid was determined by the atomic-absorption method and manganese in the conversion coating was calculated thieref rom.

in the conversion coating W /Wc X 100 WC =W1-w 2

/S

11= A. M/S wherein 11stands for weight of plate before chromic acid treatment; 11stands for weight of plate after chromic acid treatment; S is surface area (m 2) of plate.; Wc is the coating weight pe r square meter (g/m )2 A-stands for volume ofchromic a6id solution used; M stands for amount of Mn determined by atomicabsorption method and WM stands for amount of Mn in unit ae(m2) of coating.

OS

S.

@5 0O @5 0

S

@0

S

5*5

S.

S S

S

OS

S S

S.

5 5

S.

55

S

SOS S 'd~

S.

S

.S*

.S 0 5 0 5 S@ 24

S

a C Corposition of Acidic Aqueous Ex.XV Ex.XVI Ex.XVfl solution~poiflts PO 4 14.0 14.0 14.0 Mn 0.8 2.0 0.8 mi 0.3 N0 2 0.05 0.06 0.06 112 02 NO 3 404.0 '.0 CIO 1.5 1.5 1.5

BF

4 Fe(III) Total Acidity (point) 17.5 19 18 Acidity of Free Acid 0.7 0.7 0.7 point Spraying f pressure 0.8 0.8 0.8 (Kg/cz, Table 3 EX.XVIt 0.068 4.0 .56 EX. I 14.0 2.0 0.3 0.06 4.0 EX.XX EX.XXI EX.XXII 1.0 0.7 1.2 14.0 10.0 20.0 U.8 0.3 4.0 18 0.

0.0 4.0 18 0.8 0.3 0.06 24 0.7 J 0.7 0.7 0.6 0.7 0.8 0.8 0 0.8 .8 0.8

S

*5 5 4, S S S I' S. *5 S S S S S S. S S S S S S S Table 3 (continued) Componi U on[ of Acidic Aqueous Ex.XXIII Ex.XXIV EY.XXVI EX.XXVII EX.XXVIII EX.XXIX EX.XXX EX.XXXI solutionp i00 mts Zn 1.0 1.2 0.69 0.8 1.0 1.0 3.0 0.1 PO0q 14.0 20.0 11.4 14.0 14.0 14.0 20.0 Mn0.8 0.8 0.5 0.3 0.8 0.8 Ni 0.3 0.3' 0.38 0.5 0.3 0.3 0.3 N0 2 0.08 0.06 0.07 0.08 0.06 o.os 0.06 0.06 H2 02 NO 3 4.0 4.0 1.6 3.0 4.0 4.0 4.0

CIO

3 2.5 1.49 0.5 1.5 1.5 1.5 0.3 OF I 0.8-- Fe(IIH) Total Acidity (point) 18 241 14.5 17 17 17 26 8 Acidity of Free Acid 0.7 0.7 0.6 0.7 0.7 0.7 0.7 0.2 point S p i n y p r c s s u r e 0 (Kg/cm 4 0.8 0.80.080808 In Exaple XXV the same composition as given (15 sec.)- spraying (105 sec.) was used.

in Example XV was used, but intenuittent sprayingj spraying.1b sec) -stand

C

CC C C C C C C TABLE 4 M Vetal Test item EX.XV EX.XVI EX.XVII EX*XVIII EX.XIX EX.XX EX.XXI i-ot Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness dipped 2 density density density density density density density zinc Film weight(g/m )2.6 2.2 2.4 2.5 2.2 2.6 2 .3 alloy Brine spray plated (av. in mm) 2.5 2.0 1.5 1.5 1.5 1.5 on Adhesivity steel 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 plate 1 mm cuts 100/100 100/100 100/10G 100/100 100/100 100/100 100/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated 2 density density density density density density density zinc on Film weight(g/m )2.0 1.6 1.8 1.9 1.9 1.7 1.8 steel Brine spray plate (av. in mm) 3.5 3.0 2.5 2.0 2.0 3.0 Adhesivity 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 1 mm cuts 80/100 90/100 95/100 100/100 100/100 100/100 100/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated 2 density density density density density density density zinc Film weight(g/m )2.6 2.3 2.5 2.6 2.2 2.4 2.4 alloy Brine spray on (av. in mm) 2.0 2.0 2.0 1.5 1.5 2.0 steel Adhesivity plate 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 1 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 Cold Film appearance good evenness good evenness good evenness good evenness, good evenness good evenness good evenness rolled 2 density density density density density density density steel Film weight(g/m )1.8 1.5 1.8 1.8 1.6 1.8 1.8 plate Brine spray (av. in mm) 2.0 1.5 1 1.5 1.0 1.5 1.5 Adhesivity 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 1 em cuts 100/100 100/100 100/100 100/100 100/1 00 100/100 100/10 Spot rusting in mm) 0.96 1.00 1 0.98 0.91 0.96 0.97 0.96

S

0 0 0 a o f* o S a a i a S S 6 *A E S TABLE 4 (continued) Metal Test Item EX.XXIII EX.XXIV EX.XXV EX.XXVI EX.XXVII EX.XXVIII EX.XXIX Hot Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness dipped density density density density zinc Film weight(g/m 2 2.2 2.0 2.2 3.5 3.6 3.2 3.4 alloy Brine spray plated (av. in mm) 1.5 3.0 1.5 5.5 3.5 4.0 on Adhesivity steel 2 mm cuts 100/100 100/100 100/100 35/100 58/100 68/100 52/100 plate 1 mm cuts 100/100 100/100 100/100 0/100 0/100 0/100 0/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness plated density density density density Cr 2 zinc on Film weight(g/m 2 1.8 1.7 1.8 3.0 2.8 3.0 2.8 O steel Brine spray 1 7 j plate (av. in mm) 2.5 4.0 2.0 10.5 6.5 6.0 cD Adhesivity ;C 2 mm cuts 100/100 90/100 100/100 0/100 24/100 33/100 25/100 1 mm cuts 95/100 80/100 100/100 0/100 0/100 0/100 0/100 Electro- Film appearance good evenness good evenness good evenness good evenness good evenness good evenness good evenness P plated density density density 4, density L o zinc Film weight(g/m 2 2.3 2.2 2.0 3.4 3.2 2.9 I alloy Brine spray o. c on (av. in mm) 2.0 2.5 1.5 5.0 3.0 3.0 C -s steel Adhesivity C plate 2 mm cuts 100/100 100/100 100/100 20/100 64/100 52/100 48/100 SC F1 mm cuts 100/100 95/100 100/100 0/100 8/100 12/100 6/100 SCold Film appearance good evenness good evenness good evenness blue colour good evenness good evenness good evenness rolled density density density density density density density steel Film weight(g/m 1.6 1.5 1.6 0.7 2.5 2.3 2.4 S plate Brine spray (av. in mm) 1.5 2.0 1.02 4.5 2.0 2.0 Adhesivity 2 2 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 S 1 mm cuts 100/100 100/100 100/100 100/100 100/100 100/100 100/100 Spot rusting Cave. in mm) 0.98 0.98 0.87 3.10 1.10 1.30 1.30 .1 L m

S

S

i* ego...

0 *0: @0 0. C

SS

06 0 0 SSS S @0 CSc

S.

0@ 0 0

B

Tuble 4 (continued) Petal Test item EX.XY111 EX.XXX EX.XXXI Hot Film appelarance good evenness good evenness good evenuess dipped density zinc Film eightGJ/m 2.4 3.7 alloy Brine spray plated (ave.in mm) 2.5 4.0 on Adliesivity steel 2 mm cuts 100/100 0/100 60/100 plate 1 Dmm cuts 100/100 0/100 0/100 Electro- Film appearance good evenness good evenness good evenness plated density zinc on Film veight(g/m 2 1.9 3.0 1.8 steel Brine spray plate (ave.in mm) 3.5 8.6 Adhesivity 2 mm cuts 100/100 0/100 34/100 1 mm cuts 95/100 0/100 0/100 Electro- Film appearance good evenness good evenness good evenness plated density zinc Film veight(g/m 2.2 3.6 2.2 alloy Brine spray on (ave.in mm) 2.5 3.0 steel Adhesivity plate 2 mm cuts 100/100 0/100 68/100 1 mm cuts .100/100 0/100 12/100 cold Film appearance good evenness good evenness yellow rust rolled density uneven steel Film veight(g/m 1.2 2.2 1.1 plate Brine spray (ave.in mm) 2.0 3.5 Adhesivity 2 mm cuts 100/100 0/100 80/100 1 mmin cuts 100/100 0/100 30/100 Spot rusting (ave.in mm) 1.00 4.52 5.02 20

Claims (10)

1. A process for phosphating a metal surface comprising contacting the metal surface with an acidic aqueous solution comprising: from 0.5 to 1.5 g/l of zinc ion; from 5 to 30 g/l of phosphate ion; from 0.6 to 3 g/l of manganese ion; and a conversion coating accelerator wherein said contact is carried out by spraying the metal surface with the solution. S *5*

2. A process according to claim 1 wherein the solution comprises: S from 0.7 to 1.2 g/l of zinc ion; from 10 to 20 g/l of phosphate ion; from 0.8 to 2 g/l of manganese ion; and a conversion coating accelerator.

3. A process according to claim 1 wherein from 0.1 to 4 g/l of nickel ion is also present in the solution.

4. A process according to any one of claims 1 to 3, wherein the conversion coating accelerator in is at least one of the following: i) from 0.01 to 0.2 g/l of nitrite ion; ii) from 0.5 to 2 g/l of m-nitrobenzene sulfonate ion; and iii) from 0.5 to 5 g/l of hydrogen peroxide. Ukhmom bift- 31 A process according to claim 4, wherein the solution also contains from 1 to 10 g/l of nitrate ion.

6. A process according to claim 4, wherein the solution also contains from 0.05 to 3 g/l of chlorate ion.

7. A process according to any one of the preceding claims, wherein the contacting is carried out at a temperature in the range of from 400 to 70 0 C. S. 8. A process according to any one of the preceding claims, wherein the contacting is carried out for at least seconds.

9. A process according to any one of claims 1 to 7, wherein the contacting is carried out by a spray treatment for from 2 to 15 second, followed by a dip treatment for at least 15 seconds. 1o 0. A process according to any one of claims 1 to 7, °oo° *o wherein the contacting is carried out by one to three intermittent spray cycles, each cycle consisting of first spraying for 5 to 30 second, then discontinuing spraying for too* at least 5 seconds, and then finally spraying again for 5 to °ooro S 30 seconds, wherein the total spray treatment time for each .i cycle is at least 40 seconds.

11. A process according to claim 1 wherein the metal surface includes both an iron-based surface and a zinc-based surface.

12. A process according to claim 1, wherein following said process, the metal surface is rinsed and electrocoated. r~m3 32

13. An aqueous concentrate, which upon dilution with water forms a solution for use in the application of a conversion coating to iron-based and/or zinc-based metal surfaces, in accordance with the process of claim 1, comprising zinc ion, phosphate ion, and manganese ion in a weight proportion of 0.5 to 1.5 5 to 30 0.6 to 3. DATED this 12th day of September 1990. NIPPON PAINT COMPANY LTD. ee I SO WATERMARK PATENT TRADEMARK ATTORNEYS THE ATRIUM 290 BURWOOD ROAD HAWTHORN, VICTORIA 3122 AUSTRALIA e** S DBM/AB/CH (1,3)