US2658266A

US2658266A - Laminated coating

Info

Publication number: US2658266A
Application number: US303104A
Authority: US
Inventors: Rose Arthur H Du; John D Little
Original assignee: Harshaw Chemical Co
Current assignee: Harshaw Chemical Co
Priority date: 1952-08-07
Filing date: 1952-08-07
Publication date: 1953-11-10
Anticipated expiration: 1970-11-10

Description

Nov. 10, 1953 A. H. DU ROSE ETAL 2,658,256

LAMINATED coATiNC Filed Aug. 7, 1952 CHROM um WIIIIIIIIIIIIII NICKEL ICKEL A. H. DUROSE INVHVTOR.

J D- LITTLE Patented Nov. 10, 1953 stanzas;

ar 9 oil-"tips.-

Bay Village; Ohio; assignorretm The Hal-shawl Chemical Company, CleveltllipOhIlWfilBOM- ration of {Ohio Application August 7; 1952: Serial No;- 303,104

'Iliis'- invention relates'to the production of protective and decorative-electrodeposited coata ings -on base =metals which would otherwise-cor rode or exhibit an unattractive appearances More-specifically, the invention relates-tomultiple -layer protective and decorative coatings adapted to be applied over'steel:orotherbase metalibyelectrodeposition successively-from" dif ferent plating solutions.

The most common protective anddecorative coating heretofore used consists of chromium-over nickel applied;. directly on the base metal to a thickness of about a thousandth of an inch or more, or'chromium over nickel applied over a coating of .copper. These nickel-ortnickel-over copper coatings, when applied to a sufiicient thickness ;.and :builed, or when thenickelisappliedifrom a solution containing a. brightening; addition agent; are quite satisfactory for-chromium-plating. Nickel, however, is expensive-and sometimesadifficult to obtain. A need therefore exists for a-protective and decorative coating having substantially the protective anchdecorative; effect of nickel but which can be. produced at a lower cost and from materials which arelessa expensive and less difficult to obtain.

Various-lmetals have been consideredras replacements for nickel, but difficulties-rhave'alwaysz been encountered. Among the other: metals which have: been considered, lead is attractive from the standpoint of cost, but is soft and-rdifflcult to buff'to a. bright finish. Antimony also has been seriously considered, since it is harder than lead, afiords good protectionagainst corrosion; and is readily bufied. Like nickel}. antimony will' tarnish if exposed to outside atmospheres-and; should therefore be protected. Itwanamobvious procedure to try protecting an antimony deposit by? applying a chromiumldeppsitathereover in accordance with the practiceain'; nickel, 40 plating, chromium over nickel over steellbeing a very common type of coating for automobile trim, plumbing fixtures and many other: uses. When, however, it was attemptedztoi electrodeposit chromium on a bright (image-reflecting) antimony-surface it was found that the sresulting chromium deposit was not bright.

Prior tothe present invention itwasdiscovered that a bright. chromium deposit can beia-ppliedu over a bright antimony surfacerbyinte-rposing betweensuchantimony surface and therchromium a very thin nickel (or equivalent) deposit. Such nickel-deposit, it was discovered could be exceedinglytthi-n, for example as thinnas-=0.00t2:s mil (0.000002 of an inch) and musttnotzbervery thick. Thenickel deposit could be produced in any of varioussnickel plating SOIlltlOllSeSllQh as the Watts bath. Deposits from the Watts'tnickel solution ona bright antimony,surfacawereafound to -be briglit up tir-a thick ness': 013 033 mil. A's heavier deposit of nickel; for: example such as" normally: used for automobile decoration; 'tl'iat is; a dpcsit in theorder oi one' mil in tliickness; was not satisfactory for use 1 between: the anti mony and chromium; Siwl'i' deposits exliibflt poop adherence; even tend' to hake off after tl-ie= chromium" deposit isapplied It lias nowbeen discovered in accordance-with" the-=- present invention that in the case of the-s aoove describedplating sequence, that is; chro' ium over a nickel flaslrovevbriglit antinmnw over lead or equivalent' oven-steel; ai mark edly increased' resistance -to cowrosion is obtained ii at flash of nickel-is applied to tlie steel andthem followed in turn zby leadi. b'rlglit' antimony; a nickel flash' amd chromit'n'rr;- In" other words a bright l1 and" liiglily corrosion resistant -coatingis obtained by the new of chromium over a nickel flash over brig-ht antiinony overladfirver a nickel' flash on a steel object to'-be-coated2 Tfie lad layer may be omitted if the steel is:;.mugliened before applicationof thenickelflash thereon, but the conditions are more critical and 1 results not" reliable. v

Ordinarily; the bright antimony surfacewillhave been I produced by: bufllngand then thor oughly cleaning anelec-trodeposit of antimony; the=production of which asan adherenficoating on steelis known to the art. For-example; Bloom (U3 Patent No; 2,389,131)* describes a metliodof "etching the =steel and"platingon tlie' resultingi' surface fr'om-an antimony trifluoride b'atli con tainl-ng= a= monovalent fluoride and operating; at"

form any part of the present invention. Leach,

nickel, chromium, antimony, etc: platingare well established artsand no novel plating; solutions" areessential to" the realization of the'present invention:

It the-primary object is to *form a" protective and-*decorative coating' onsteel; brass, copper-"or" the like; a" very excellent procedure isto' apply" first a flashof nickel or cobalti then an" elect'rc deposit of "lead;- tin, silveror'alloysthereof wliich' are"easily-*applied over-nickell- A'dlierent-antialloy electrodeposits in the form of adherent" coatings-which can -beweadily bufEd to-a high lustre: O'n theabuitd antimony, there-maybe v tlxenaappliedz avery thin coating of: nickel; or.

cobalt, or less desirably, zinc, copperywhitesbrass: or: iron; Qverr? thee resulting: thine. depositsthere isaappliedr. amelectrodepositeda coating 2 chrov mium, suitably of a thickness of the order of 0.01 mil, which will not be dull, as in the case where it is plated directly on polished antimony, and which will not cause a separation of the thin nickel (or the like) deposit from the antimony, as when relatively heavy deposits of nickel are applied on the antimony and followed by chromium.

So far as I am aware, no one has heretofore suggested the plating sequence herein disclosed having the protective value as above indicated. It is perhaps surprising that a chromium deposit would not turn out bright when applied over highly polished antimony, but that has been found to be what happens; and while it would be expected from nickel plating practice that a bright chromium deposit could be applied on a bright nickel surface, it is surprising that an ultrathin layer of nickel but not a heavy layer thereof would result in overcoming the tendency 2 of chromium to plate dull over polished antimony and at the same time retain satisfactory adhesion in the case of thin layers (but not in the case of thick layers) of nickel or cobalt. It is surprising also that an ultrathin layer of nickel or cobalt applied between the steel and the lead deposit or between roughened steel and the antimony deposit would result in extraordinarily improved corrosion resistance, far beyond what could be expected merely from the thickness of such a nickel flash itself.

In the accompanying drawing, the figure is a schematic representation of a multiple-layer deposit according to the invention, wherein the thicknesses are greatly exaggerated, and wherein the bufling step is indicated by a schematic representation of a buifing-wheel applied on the surface which is buffed.

In the drawing, the numeral I indicates the base metal to be coated, which as indicated, may

be steel, copper brass, or the like. Electrodeposited on the base metal body i0 is a thin layer II of nickel or cobalt which may be of a thickness from 0.06 to 0.1 mil. This layer can be heavier, say up to .5 mil, but it is not necessary to use any more nickel or cobalt than indicated. Electrodeposited on the nickel flash coating is the optional layer I2 of lead, which, it is to be understood, may be omitted if suitable care is taken to apply a strongly adherent coating of antimony on the nickel or cobalt flash coating. Also the lead coating ll may be replaced by tin or silver. The antimony deposit l3 must be strongly adherent as it will be if applied over lead, tin or silver, and should be of a thickness great enough that, upon being buffed, there is no danger of cutting through and exposing the underlying layer. The antimony deposit normally may be of a thickness of about 0.3 mil, and preferably is of a thickness of the order of 0.5 to 2.0 mils. A thickness from 0.75 to 1.5 mils should prove adequate for any reasonable amount of buffing. The antimony deposit is buifed to a bright finish, as indicated by the schematic indication of a buffing wheel M in contact with its surface, and thereafter there is applied the ultrathin coating l5 of nickel or cobalt (less desirably copper, zinc, iron or white brass). This coating may be of a thickness from .001 to .05 mil, but preferably is from 0.002 to 0.03 mil in thickness. The chromium deposit [6 is applied over the ultrathin coating I5 of nickel, cobalt or the like and may be of a thickness from 0.001 to 0.02 mil.

While the nickel flash under chromium and over bright antimony on lead on steel is not per se a part of the present invention, the fact that its deleterious effect on corrosion resistance can be overcome by a flash of nickel between the steel and the lead is believed not to have known heretofore. The effect is marked and goes beyond any mere additive effect of the thin nickel coating. It was found for example that .01 mil of chromium on 1.0 mil of antimony (buffed) on .2 mil of lead on steel exhibited a salt spray resistance of 100 hours but was not bright. Applying .003 mil of nickel or cobalt over the buffed antimony and under the chromium gave good brightness and adherence but the salt spray resistance was reduced to 40 hours. Applying .06 mil of nickel between the steel and the lead in addition to the nickel flash between the antimony and the chromium, the salt spray resistance went up to 100 hours. This amount (0.06 mil) of nickel on steel as the only coating would resist salt spray only from 2 to 4 hours.

Cobalt in similar thicknesses was found to be the equivalent of nickel for the flash on the steel except for its higher cost.

Plating solutions suitable for the electrodeposition of antimony, lead, nickel, cobalt, zinc, iron,

copper and white brass are as follows:

(1) SbFs 250 g./l. NHiF 200 g./l. pH 4.5 Temperature 130 F.

(2) SbF3 NH4 2S04 400 g./l. pH 1.5 Temperature 130 F.

(3) Pb(BF4)2 33.5 oz./gal. HBF4 10.7 oz./gal. H3130: 3.0 oz./gal. Glue .03.06 oz/gal. Temperature Room (4) NiSO4.6H2O 250 g./l.

NiC12.6H2O 35 g./l.

H3303 35 g./l. pH 4.0 Temperature 120 F.

(5) NiS04.6H2O 100 g./l.

NiClz.6HzO g./l. H3303 g./l. pH 3.0 Temperature Room The antimon surface must be well cleaned before nickel is applied.

(6) C0Cl2.6H2O 100 g./l.

NH4F.HF 20 g./l. pH 3.0 Temperature 130 F. ('7) ZI1(CN)2 g./l. NaCN 42 g./l. NaOH 79 g./l. NazS 0.75 g./l. Temperature 80 F. (8) FeSO4.7H2O 200 g./l.

NaBFi 40 g./l. pH 3.0 Temperature F. (9) CuCN 22 g./l. Free Cyanide 7.5 g./l. Water Remainder pH 12 Temperature F. (10) Zn(CN)z 60 g./l. Cu(CN)2 14 g./l. NaOH 60 g./l. NaCN 52 g./l. NazSOa 0.48 g./l. Temperature 90 F.

Having thus described the invention, what is claimed is:

1. A process comprising electrodepositing on a metallic surface of the class consisting of steel, brass and copper a layer of a metal of the class consisting of nickel and cobalt and mixtures thereof of a thickness from .02 to .2 mil, forming on said layer an adherent coating of a metal of the class consisting of lead, tin and silver, said coating being applied by electrodeposition, forming on said last mentioned coating a bright coating of electrodeposited antimony, forming on said bright antimony coating a film of a metal of the class consisting of nickel, cobalt, zinc, iron, white brass and copper of a thickness from .001 to .05 mil, said film being applied by electrodeposition, and electrodepositing a layer of chromium over said film.

2. A process comprising electrodepositing on steel a layer of nickel of a thickness from .02 to .2 mil, forming on said layer of nickel an adherent coating of lead, said coating being applied by electrodeposition, forming on said last mentioned coating a bright coating of electrodeposited antimony, forming on said bright antimony coating a film of nickel of a thickness from .001 to .05 mil, said film being applied by electrodeposition and electrodepositing a layer of chromium over said film.

3. A process comprising electrodepositing on a metallic surface of the class consisting of steel, brass and copper a layer of a metal of the class consisting of nickel and cobalt and mixtures thereof of a thickness from .02 to .2 mil, forming on said layer an adherent coating of a metal of the class consisting of lead, tin and silver, said coating being applied by electrodeposition, forming on said last mentioned coating a bright coating of antimony, said coating being applied by electrodeposition and then buffed to brightness, forming on said bright antimony coating a film of a metal of the class consisting of nickel, cobalt, zinc, iron, white brass and copper of a thickness from .001 to .05 mil, said film being applied by electrodeposition and electrodepositing a layer of chromium over said film.

4. A process comprising electrodepositing on steel a layer of nickel of a thickness from .02 to .2 mil, forming on said layer of nickel an adherent coating of lead, said coating being applied by electrodeposition, forming on said last mentioned coating a bright coating of antimony, said coating being applied by electrodeposition and then bufied to brightness, forming on said bright antimony coating 2. film of nickel of a thickness from .001 to .05 mil, said film being applied by electrodeposition and electrodepositing a layer of chromium over said film.

5. A laminated, metallic, bright, protective coating on a metal base of the class consisting of steel, copper and brass consisting of a firmly adherent layer of a metal of the class consisting of nickel, cobalt and mixtures thereof of a thickness from 0.2 to .2 of a mil, a layer of the class consisting of lead, tin and silver of a thickness from 0.1 to .7 mil overlying and adherent to said last mentioned layer, a firmly adherent layer of antimony on said last mentioned layer and having a bright surface, a film of a metal of the class consisting of nickel, cobalt, zinc, iron, white brass and copper of a thickness from .001 to .05 mil firmly adherent to said bright surface and a layer of fully bright, unburied chromium of a thickness from .003 to .03 mil firmly adherent to said film.

6. A laminated, metallic, bright, protective coating on steel consisting of a firmly adherent layer of nickel of a thickness from .02 to .2 mil, a layer of lead of a thickness from 0.5 to .7 mil overlying and adherent to said last mentioned layer, a firmly adherent layer of antimony of a thickness from 0.0003 to 0.002 of an inch on said last mentioned layer and having a bright surface, a film of nickel of a thickness from .001 to .05 mil firmly adherent to said bright surface and a layer of fully bright, unbufied chromium of a thickness from .003 to .03 mil firmly adherent to said film.

ARTHUR H. DU ROSE. JOHN D. LITTLE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,314,603 Mott Sept. 2, 1919 1,738,748 Wirshing et al. Dec. 10, 1929 1,792,082 Fink Feb. 10, 1931 1,918,159 Weisberg et al July 11, 1933 2,039,068 Domm Apr. 28, 1936 2,428,033 Nachtman Sept. 30, 1947

Claims

5. A LAMINATED, METALLIC, BRIGHT, PROTECTIVE COATING ON A METAL BASE OF THE CLASS CONSISTING OF STEEL, COPPER AND BRASS CONSISTING OF A FIRMLY ADHERENT LAYER OF A METAL OF THE CLASS CONSISTING OF NICKEL, COBALT AND MIXTURES THEREOF OF A THICKNESS FROM 0.2 OF A MIL, A LAYER OF THE CLASS CONSISTING OF LEAD, TIN AND SILVER OF A THICKNESS FROM 0.1 TO .7 MIL OVERLYING AND ADHERENT TO SAID LAST MENTIONED LAYER, A FIRMLY ADHERENT LAYER OF ANTIMONY ON SAID LAST MENTIONED LAYER AND HAVING A BRIGHT SURFACE, A FILM OF A METAL OF THE CLASS CONSISTING OF NICKEL, COBALT, ZINC, IRON, WHITE BRASS AND COPPER OF A THICKNESS FROM .001 TO .05 MIL FIRMLY ADHERENT TO SAID BRIGHT SURFACE AND A LAYER OF FULLY BRIGHT, UNBUFFED CHROMIUM OF A THICKNESS FROM .003 TO .03 MIL FIRMLY ADHERENT TO SAID FILM.