CA1210732A

CA1210732A - Composition and process for the electrodeposition of zinc-nickel alloy deposits

Info

Publication number: CA1210732A
Application number: CA000409819A
Authority: CA
Inventors: Masaaki Kamitani; Hidenori Tsuji
Original assignee: Ebara Udylite Co Ltd
Current assignee: JCU Corp
Priority date: 1981-08-21
Filing date: 1982-08-20
Publication date: 1986-09-02
Also published as: DE3231054A1; GB2104920B; AU534369B2; NL184070C; NL184070B; NL8203266A; IT8268027A0; AU8705682A; BR8204892A; IN157700B; ES8308366A1; FR2511707B1; ES515149A0; GB2104920A; IT1156492B; KR840001231A; JPS6012434B2; KR880001584B1; MX158623A; FR2511707A1

Abstract

ABSTRACT OF THE DISCLOSURE
In accordance with the present invention there is provided an aqueous electroplating bath hav-ing a pH of from about 4.7 to 8.0, which bath contains at least 10 g/l zinc, 15 g/l nickel, at least 20 g/l ammonium, ions, a weight ratio of nickel/zinc, of at least 0.5 and a brightening/grain refining amount of a nonionic polyoxyalkylated surfactant. Electrolysis of this electroplating bath produces a uniform, fine grained zinc-nickel alloy electrodeposit which is at least semi-bright in appearance and which contains at least 5% by weight of nickel. The thus-produced nickel alloy electrodeposit provides excellent corrosion re-sistance to the substrate, such as steel, on which it is plated.
In a preferred embodiment the electroplating bath of the present invention may also contain an aro-matic aldehyde or aromatic ketone as a secondary brightener to produce a full, mirror bright deposit.
Alternatively, or in addition to the secondary bright-ener, the bath may contain a lower alkyl carboxylic acid or salt thereof, as an auxiliary low current density area brightener.

Description

12~32 This invention relates to the electrodeposi-tion of zinc-nickel alloy deposits and, more particu-larly, relates to compositions and processes for the electrodeposition of bright~ uniform zinc-nickel alloy deposits having improved corrosion resista~ceO

BACKGROUNI) OF THE INVENTION
_.
It has long been recognized that zin~-nickel alloy electrodeposits will provide excellent corrosion resis~ance to the substrates, such as steel, to which 1~ they are applied. In many instances the corrosion re-sistance of zinc-nickel alloy electrod~posits are su-perior to that obtained from either a nickel or a zinc electrodeposit~ Accordingly, consi~erable effort has been made to take advantage of this superior corrosion resistance.
In general, it has been found to be extremely difficult to obtain a uniform, bright zinc~nickel alloy electrodeposit Typically, the electrodeposits obtain-ed from these prior art processes have been matte de-posits which were grey to black in color. The addi-tion, to these electroplating baths, of one or more brightening agents known to be effective in nickel plating or in zinc plating has not produced a bright, uniform zinc-nickel alloy electrodeposit. Consequent-ly, such alloy electrodeposits have been utilized ex-tensively only in continuous plating processes, partic-ularly for steel s~rip or wire and the like, in which a high degree of brightness and uniformity in the elec-trodeposit are not required~

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rlypical prior art processes for strip plating with zinc-~lickel alloys are disclosed in U.S. Patents ~,282,073i 4,313,802; 3,558,442; 3,~20,754; and 2,419,231; G.B. Patent 5481~4 and Japanese Patent Disclosure 28533/1976 published March 10, 1976 to Matsushita Denki Sagyl Co. In addition -to the inability of these processes to produce a bright, uni-form alloy electrodeposit, they are typically operated at a relatively acidic pH, e.g., a pH within the range of about 1-4. Such acidic electroplating baths are not only more corrosive to the equipment and environment but, also, are more difficult -to maintain. This is due to the na-tural tendency of the pH to rise in the electroplating bath during the electrolysis process. This necessitates the continual addition of acid to the electroplating bath in order to control it and maintain it within the desired operating pH
range.

Moreover, the prior art processes for strip plat-ing with zinc-nickel alloys typically utilize a sulphate or ~0 mixed sulphate-chloride matrix or/ in the case of the pro-cess of the Japanese Patent Disclosure, a cyanide matrix.
In regard to the latter, such electroplating baths, in addi-tion to being toxic, present significant ecological problems and require expensive waste treatment equipment. In regard to the electroplating baths which utilize a sulphate con-taining matrix, these exhibit low current efficiencies, due to the poor conductivity of the sulphate ions, thus requir-ing more energy for the pla-ting operation. ~lthough this may not be a serious problem in these continuous plating processes, due to the relatively simplistic shape, e.g.
strip or wire, of the substra-te being plated, it becomes very significant where it is desired to produce a bright, uniform deposit on a more complex shaped subs-trate , . . j .
~ 2 3 ~l2~)'73~

An attempt to overcome these difficulties is described in U.S~ Patent 4,285, 802. As set forth in this patent, a bright zinc-nickel alloy electrodeposit containing up to about 5% nickel, is produced from a S chloride matrix electroplating bath which contains from about 10 - 100 grams per liter of z;nc and from about 0.01 - 10 grams per liter of nickel. As brightener additivesr the electroplating baths of this patent con-tains a nQniOniC polyoxyalkylated surfactant and an aromatic aldehyde. Although the patent discloses an operable pH range from about 3.0 - 6.9, in actual prac-- tice, it has been found that fully bright zinc-nickel alloy deposits are not obtained in this process when the pH is in excess of about 4.5. Additionally, the maximum nickel content of the alloy deposit of S% does not provide the desired level of corrosion protection to the substrate. Accordingly~ the process of this patent provides, at best, only a partial solution to the problems o~ the prior ar~.
The present invention thus provides an improved electroplating bath and process for the electrodeposition of bright, uniform zinc-nickel alloy deposits The present invention also provides an improved electroplating bath and process which will produce a bright, uniform zinc-nickel alloy electro-deposit having improved corrosion resistance.
The present invention again provides an improved bath and process which will operate at a less acidic pH than has been possible in the prior art to produce a bright, uniform zinc~nickel allcy electrodeposit having excellent corrosion resistance.

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The present invention will be illustrated y way o~ the ac~onlpanying drawing drawing:-Fig~ 1 ls a graph showing the results of the film thicklless distribution measurements f~relectrodeposits obtained with the present inverltion and with the prior art.

SUMMARY OF THE INVENTION_ In accordance with the present invention there is provided an aqueous electroplating bath having a p~ of from about 4.7 to 8.0, which.bath contains at least 10 g/l zinc, 15 g/I nickel, at least 20 9~1 ammonium, ions, a weight ratio of nickelJzinc, of at least 0.5 and a brightening/grain refining amount of lS a nonionic polyoxyalkylated surfactant. Electrolysis of this electroplating bath produces a uniform, fine-grained zinc-nick~l alloy electrodeposit which is at le~st semi~bright in appearan~e and which contains at least 5~ by weight of nickel. The thus~produced nickel alloy electrodeposi~ provides excellent corrosion re-s stance to the substrate, such as steel, on which it is plated.
In a preferred embodiment the electroplatin~
bath of the present inven.tion may also contain an aromatic aldehyde or aromatic ketone as a secondary brightener to produce a full, mirror bright deposit.
Alternatively, or in addition to the secondary bright-ener, the bath may contain a lower alkyl carboxylic acid or salt ~hereof, as an auxiliary low current den-sity area brightener.

DETAILED DESCRIPTION OF THE INVENTION
More specifically, the zinc~nickel alloyelectroplating bath of the present inventioll will ~ILZ~'7~

contain at least 10 grams per liter of zinc up to the maximum solubility of zinc in the bath, with an amount of zinc from about 10 to about 90 grams per liter being preferred. The nickel content of the electroplating bath will be at least 15 grams per liter up to the max-imum solubility of nickel in the bath, with an amount of nickel from about 15 to about 60 grams per liter being preferred. The weight ratio of nickel/zinc in the bath will be at least about 0O5 and preferably from about 0.5 to about 10 D
The zinc and nickel are typically introduced into the bath, at least when the bath is initially formulated, as the respective chlorides. Although an~
bath soluble chlorides of zinc and nickel may be used, the zinc is typically added as zinc chloride (ZnC12) and the nickel as nickel chloride hexahydrate (NiC12.6~20). During the operation of the electro-plating process, the desired amount of zinc and nickel will often be maintained in the bath by the use of zinc and nickel metal anodes and or zinc-nickel alloy anodes, which dissolve in the bath during electrolysis.
Where, however, the amount of zinc and nickel provided by the anode dissolution in the bath is not sufficient to maintain the desired zinc and nickel levels, these levels may be maintained by the supplemental addition of the respective zinc and nickel chlorides to the bath.
The electroplating baths of the present in-vention will also contain at least about 20 arams per liter of ammonium ions up to the maximum solubility of the ammonium ions in the bath, with amounts within the Lange of about 20 to about 120 grams per liter being prefered. As with the zinc and nickel, the ammonium ions are added to the bath as the bath soluble ~2~

11,044 chloridf:, preferably ammonium chloride (NH4Cl). Al-though it has been found to be necessary to maintain an ~mmonium ion content in the bath of at least about 20 grams per liter, the maximum amount of ammonium ions has not been found to be critical, provided the amount of ammonium ions in the electroplating bath are suffi-cient to maintain the zinc and nickel ions in the solu-tion. In general, it has been found that whore the minimum amounts of zinc, nickel and ammonium ions of 10, 15 and 20 grams per liter~ respectively, are not maintained and or where the weight ratio of nickel/zinc is not at least about 0.5, satisfactory zinc-nickel alloy deposits, in terms of uniformity and brightness~
cannot be obtained. Moreover, acceptable deposits and lS platinq operations will not be achieved if the zinc, nickel and ammonium components of the bath are intro-duced as the sulphates, rather than the chlorides.
In order to providc suffic;e~t conductivity in thc present electroplating baths, the total chloride content of th~se baths should be at least about 90 grams per liter and, preferably~ is from about 150 to about 300 grams per liter. Where the desired total chloride content of th~ bath is not achieved through the addition of the zinc, nickel and ammonium chlor-ides, other bath soluble chloride compounds may be aad-ed to achieve the desired total chloride content~ Typ-ically, such bath soluble chlorides will be potassium chloride or sodium chloride, with potassium chloride being particularly preferreL.
In addition to the zinc, nickel and ammonium components, thc novel electroplating baths of the pre-sent invention will also contain a nonionic polyoxy-alkylated surfactant. The nonionic polyoxyalkylated surfactant will be present in an amount at least suffi-~2~7~

cient to provide grain refinement of the zinc-nic~el alloy electrodeposit and produce a deposit which is at . least semi-bright in appearance. Typically, this ma-terial will be present in the bath in an amount of at leas~ about 0.1 gram per liter up to its maximum solu-bility in the bath, with amounts within the range of about 0.1 - 200 grams per liter being preferred.
The nonionic polyoxyalkylated surfactants useful in the composition of the present invention are condensation cop~lymers of one or more alkylene oxides and another compound, in which the alkylene oxide con-tains from one to four carbon atoms and the resulting copolymer product contains from about 10 to about 70 moles of the alkylene ~xide per mole of the other com-pound. Exemplary of such other compounds which may bealkoxylated are alcohols, including linear alcohols, aliphatic monohydric alcohols, aliphatic polyhydric al-cohols, and phenol alcohols; fatty acids; fatty amides;
al~yl phenols; alkyl naphthols; aliphatic amines, in-cluding both mono and poly amines; and the like.
Examples of typical suitable surfactants ofthis type are^
A. Nonionic copolymers of ethylene oxide and linear alcohols having the following structural form-ula:
C~3 - ~CH2)x ~ CH3 O - (CH2-CH20)n ~ H
wherein x is an in~eger from 9 - 15 and n is an inte-ger from 10 - 50. Surfactants of the foregoing struc-ture are members of the Tergitol S series available from Union Carbide. Examples of those useful surfac~
tants are Tergitol Nonionic 15-S-3, Tergitol Nonionic 15-5-5, Tergitol Nonionic 15-S-7, ~ergitol Nonionic 15-S-9 and Tergitol Nonionic 15-S-12. ~ergitol is a trademark o Union Carbide Corporation.
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~2~ 73;~

B. Nonionic copolymers of ethylene oxide and phellol alcohols having the following structural formula:

2)x Ar O (CH2CH2O)n Cl-l2 CH2 O~l wherein Ar is a benzene ring, x is an integer from 6-15 and n is an integer from 10-50. Surfactants of the foregoing structure are members of the Igepol CO surfactants available from GAF Corporation. Igepol is a trademark of GAF Corpora-tion.

C. Nonionic copolymers of e-thylene oxide and coconut fatty acids or alkanol amine coconut fatty acids.
Coconut fatty acids are derived from the hydrolysis of coconut oil and generally have the following structural formula:

Cn H2n+1 COOH
wherein n is an integer from 5-17.

D. Other specific examples of nonionic polyoxy-alkylated surfactants useful in the present invention in-clude, for examplel alkoxylated alkyl phenols, e.g., non-ylphenol; alkyl naphthols; aliphatic monohydric alcohols;aliphatic polyhydric alcohols, e.g., polyoxypropylene glycol; ethylene diamine; fatty acids, fatty amides, e.g., amide of coconut fatty acid; or esters, eOg., sorbitan mono-palmitate. Exemplary alkoxylated compounds within the above classes which are commercially avai:Lable include "Igepol" CA
630, trade mark for an ethoxylated octyl phenol, available from the GAF Corp.; "Brij" 98, trade mark for an ethoxylated oleyl alcohol available from ICI America, Inc.; "Pluronic"
F68, trade mark ~or a polyoxyethylene-polyoxypropylene glycol available from BASF Wyandotte Corp.; "Surfynol" ~85, trade mark for ethoxylated 2,4,7,9-tetrame-thyl-5-decyne-4,7-.~. .,. ~
.;.

1;2~L(37~

diol available from Air Products and Chemicals, Inc.;"Tetrollic" 504, trade mark for an ethoxylated propoxylated ethylene diamine available from BASF Wyandotte Corp.; "Myrj"
525, trade mark for an ethoxylated s-tearic acid available from ICI

- 8a -. ~ ~

1~()7~
_g America, Inc.; ~Amidox~ C-5, trade mark for a poly-ethoxylated coconut acid monoethanolamide available from Stepan Chemical Co.; "Tween~ 40, trade mark ~or ~n ethoxylated sorbitan palmitate available from.ICI ~mer-ican, Inc.; Liponox NCT and OCS, trade marks for poly-oxyethylene alkylphenol ethers and polyoxyethylene alkyl ethers ~vailable from Lion Corp.; Pluronic L64, trade mark ~or polyoxyethylene polyoxypropylene glycol and Tetronic 704, trade mark f;or polyoxyethylene poly-oxypropylene ethylenediamine, both available from Pro-duct~ rhimiques Ugine-Kuhlman; and Ethomeen C/25~ trade mark for ethoxylated amines and Ethomid 0~15, trade mark ~or ethoxylated amides, both available from Akzo Chemie.
-15 Electrolysis of the electroplat;ng baths de-scribed hereinabove will produce uniform, fine.grained zinc-nickel alloy electrodeposits which are at least semi bright in appearance. While these deposits are .generally not completely mirror bright, they do have a r gr~ater mUcrocrystalline~ uniform appearance than zinc-nickel alloy deposits produced by the prior.art.
These deposits provide excellent corrosion resistance to the substrate, such as steel, to which they are applied and, thus, are useful in those ins~ances where a mirror-bright deposit is not required.
Where it is desired to produce a zinc-nickel alloy electrodeposit having mirror brightness, this may be accomplished by includi.ng in the electroplating bath an aromatic aldehyde or aromatic ketone secondary brightener~ Such secondary ~rightener is added to the bath in an amount sufficient ~o impart mirror brightness to the deposit up to the maximum solubility of the brightener additive in the bathn Preferably, -l o 12~3Z

the;e s~condary brighteners are included in the elec-troplating bath in amounts from about 0.01 to about 2 grams per liter~
Typical of the aromatic aldehydes or aromatic ketones which may be used as secondary bri~hteners are the aryl aldehydes and ketones, the ring~halogenated aryl aldehydes and ketones, and heterocyclic aldehydes and ketones. Exemplary o~ specific compounds which ma be used are ortho~chlorobenzaldeh~de, para-chlorobenz-aldehyde, benzylmethyl ketone, phenylethy~ ketone,cinnamaldehyde, benzalacetone, thiophene aldehyde, ~urfural-5-hydroxymethyl furfural, furfuryl-dene acetone, furfuraldehyde and 4-(2 furyl)-3-buten-2-one and the like~ -The electroplating baths of the present in-vention, either wi~h or without the above-described secondary brighteners, may also contain an auxillary low current density area brighteners. Suitable auxilr ~ary brighteners are the lower alkyl carboxylic acids and their bath soluble salts, wherein the alkyl group con~ains from about 1 to about 6 carbon atoms. Although ei~her the acid itself or the bath soluble salts m~y be utilized, in many instances the sodium, potassium or ammonium salts are preferred. A particularly preferred auxillary brightener for use in the present invention is sodium acetate. These auxillary brighteners are typically utilized in amounts within the range of from about O.S to about Z5 grams per liter, with amounts within the range of about 1 to about 10 sramS per liter being particularly preferred.
The pH of the electroplatlng baths of the present invention is from about 4-7 to about 8, with a pH from about 5 to about 7 bein~ particularly preferr-ed. Where the pH of the solution is below abou~ 4.7, there is poor grain refinement of the deposit and a J7~2 uniform, bright appearance is not obtained. At a pH
above about 8, the electrodeposit may become cloudy and there is a tendency for ammonia gas to be evolved from the plating bath. Maintenance of the pH of the elec-troplating bath within the desired range may be accom-plished by the addition of ammonium hydroxide, to raise the pH, or hydrochloric acid to lower the pH~
In some instances, where the bath is ope ated at the high end of the pH range, eg, at a pH of from about 7 to about 8, it may also be desirable to include a suitable ~omplexing agent in the bath to prevent pre-cipitation of the ~inc and/or nickel metal. Any suit-able complexing agent for zinc and/or nickel may be used, in an amount sufficient to prevent the precipita-tion of zinc and/or nickel from the bath. Typical ofthe complexing agents which may be used are ethylene-diamulle tetra-acetic acid, diethylenetetramine pentaacetic acid and Quadrol (N,N, N',N'-tetrakis(2-hydroxypropyl)ethylenediamune). Quadrol is a trade mark of BASF Wyandotto Industrial Chenucal Corporation.
The zinc-nickel alloy electroplating baths of the present invention are particularly suitable for u~e in rack plating processes, although, in some in-stances, they may be utilized in barrel plating pro-cesses as well. Typically, plating is carried ~ut at cathode current densities of from about 4 to about 80 amps per square foot, with a cathode current density of from about 10 to about 60 amps per square foot being particularly preferred~. During electrolysis~ the elec-troplating bath is desirably maintained at a tempera-ture within the range of about 25 to 50 degrees C., with a temperature within the range of about 30 to 40 degrees C~ being preferred. The anodes used in the electroplating process are preferably metallic zinc and metallic nickel anodes, although zinc-nickel alloy ~Zl~g73Z

anodes may be used. The relative surface area of the zinc and nickel anodes may be varied to provide the desired replacement of zinc and nickel metal in the electroplating bath. In many instances, a zinc to nickel anode ratio of about 9 to 1 has been found to be effective in maintaining the desired concentrations of zinc and nickel in the electroplating bath.
In order that those skilled in the art may better understand the present invention in the manner in which it may be practiced, the following specific examples are given.

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SPECIFIC EXAMPLES

In the following examples, the electroplating was carried out in a 267 ml ~ull Cell for 5 minutes at a current of ~ amperes and a bath temperature of 35 degrees C., using a zinc anode and a bright steel plate cathode.

.EXAMPLE 1 B~
A aqueous-electroplating~was formulated con-taining 100 g/l ZnC12, 120 gjl NiC12.6H2O, 240 10 . g/l NH4Cl and 3 g/l o ethoxylated 2,4,7,9 tetra-methyl-5-decyne-4,7-diol(Surfynol 485). The bath pH
was 5.5 and the weight ratio of nickel/zinc was Q~6.
The zinc-nickel alloy electrodeposit obtained from plating with this bath in accordance with the procedure set forth above was semi-bright and uniform in appear-ance. - -~or purposes of comparison, an electroplating bath was formulated containing 100 g~l ZnC12, 120 g/l NiC12.6H2O, and 240 gjl NH4Cl. The weight ratio Gf nickel/zinc in this bath was 0.6 and the~pH was 5~5.
The zinc-nickel alloy electrodeposit produced from the electrolysis of this bath in accordance with the pro-cedure set forth above was ash grey in appearance in the high and medium current density areas and black in the low current density area, with no evidence of brightness.

3'~
~1,044 -14-An electroplating bath was formulated con-taining 120 g/1 ~ C12, 160 g/l N;Cl2.6H2~ 250 g/l NH4Cl, S 9/1 ethoxylated 2,4,7 J 9-tetramethyl-5 decyne-4,7 diol (Surfynol 485) and 0.05 9/1 benzalace-tone. The electroplating bath had a weight ratio of nickel~zinc of 0.7 and ~ pH of 6.8. The zinc-nickel alloy electrodeposit obtained by the electrolysis of this bath in accordance with the above pro edure was uniform in appearance, and mirror bright in the medium and low current density areas with only slight stri~-tions in the high current density area.

An electroplating bath was formulated con-lS taining 20 a/l ZnC12, 150 g/l NiC12.6H2O, 15 g/l NH4Cl, 80 g/l KCl, 2 g/l polyoxyethylene aIky~phenol ether ~Liponox NCT) and 0.04 g/l benzalacetone. The weight ratio of nickel/zinc in the bath was 3.8 and ~he bath pH was 5.0~ The zinc-nickel alloy electrodeposi~
obtained by the electrolysis of this solution in accordance with the procédure set for~h above was uni-form in appearance, mirror bright in the med ium and low current density areas with only slight striatio~s in the high current density area.

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EXAMPL.E 5 :
An electroplating bath was formulated con-taining 80 g/l ZnC12, 8~ 9/l NiC12.6H2O, 180 g/l NH4Cl, 1 g/l polyoxyethylene polyoxypropylene glycol (supplied under the trade mark Pluronic L64) and 0.02 g/1 cinna-maldehyde. The weight ratio of nickel/zinc in the bath was about 0.5 and the bath p~ was 5.5. The zinc nickel alloy electrodeposit produced from this bath by electrolysi~ in accordance with the above procedure was unîform in appearance and nearly mirror bright throughoutt with only ~light clouding.

EXAMPLE 6 .

An elec~roplating bath was formulated con-taining 20 g/l ZnC12, 240 g/l NiCl2.6H20 60 g/l ~4Cl, 1 g/l pol.yoxyethylene alkylamine (supplied under the trade mark Ethomeen C/25) and 0.02 g/l ortho-chlorobenzaldehyde. The weight ra~io of nickel/zi~c in the bath was about 6.2 and the bath pH was 5.3. The zinc-nickel alloy eleco trodeposit ob1:ained by electrolysis of this bath in accordance with the above procedure was uniform in appearance, nearly mirror bright with only slight clouding.

~Z~ 3;~

EXA~lPLE 7 An electroplating bath was formula~ed con-taining 120 9/1 ZnC12, 120 g~l NiC12.6H2O, 240 g/l NH4Cl, 10 g/l ethoxylated 2,4,7,9-tetramethol-S-decyne-4,7-diol (supplied u~der the trade mark Surfynol 485) and 0.3 g/l benzalacetone. The electroplating bath had a nickel/zinc weight ratio cf about 0.5 and a pH of 5.6. The zinc-nickel alloy electrodeposit produced by the electrolysis of this bath in accordance with the above procedure was uniform in appear~nce and mirror bright over the entire surface. This electrodeposit was analyzed for nickel content and it was aetermined that the nickel conten~
of the deposit in the areas which were 2 centimeters, 5 centimeters and ~ centimeters from the high current side of the Hull Cell plate was 7.6%, 7.9% and 10.7% by weight~ respectively~

An electroplating bath was formulated con-taining 20 y/l ZnCl~t ~4~ 9/1 NiC12.6H20, 150 9/1 1~-14Cl, 2.0 g/l polyoxyethylene alkylamide (supplied under the trade mark (Ethomid O/15) and 0.1 g/l of phenylethyl ketone. The bath had a weight ratio of nickel/zinc of about 6.2 and a 2H of 6.8. The 2inc-nickel alloy electrodeposit obtained by the electrolysis of this solution in accordance with the above procedure was uniform, and mirror bright throughout, with only slight s~ria-tions in the high current density area.

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~hree electroplating baths were formulated containing 120 g/l ZnC12, 140 g/l NiC12.6H20, 240 g/l NH4Cl, 1.0 g/l benzalacetone and S.0 g/l of a nonionic polyoxyalkylated surfactant. In the first bath the sur-fact~t was polyoxyethylene alkyl e-ther (supplied under the trade maxk Liponox oCS); in the second bath the surfactant was polyoxy ethylene sorbitan pal~itate (supplied under the trade ~ark Tween 40); and in the third bath the surfactant was ethoxylated propoxy--lated ethylenediamune ~supplied under the trade mark Tetronic 704).
In each bath, the weight ratio of nickel/zinc was 0.72 and the bath pH was 5.5. The zinc-nickel alloy electrodeposits ob-tained by the electrolysis`of these three baths in accordance with the procedures set orth hereinabove were each uniform and mirror bright over the entire surface~

An electroplating bath was formulated con-taining 1~0 g/l ZnC12, 130 g/l NiC12.6H20, 200 g/l NH4C1~ 2.0 g/l sodium acetate, 5.0 gJl ethoxy~at-ed 2,4,7,9-tetra~ethyl-5-decyne-4,7-diol (suppl.ied under the trade mark (Surfynol 485), and 0.1 g/l benzalacetone. The weight ratio of nlckel/zinc in the bath was 0067 and the bath pH was 5.6~ The zinc-nickel alloy electrodeposit produced by the electrolysis of this bath in accordance with 'che above procedure was uniform and completely mirror bright over the entire surface.

EXA~IPLE lI

Using the electroplat.ing baths of Examples 1 and 3 through 10, steel plates we~e plated with a zinc-nickel alloy deposit to a thickness of 3 microns at a bath temperature of 35 degrees C. and a cathode current density of about 30 amps per square oot. The thus-plated panels were then subjected to the standard salt spray test (AS~ B 117) and it was dete ~ ned tllat, in each in-- stance, approximately 160 hours of exposure was requir-ed before red rust began to develop ~n the zinc-nickel alloy surface. Similar steel panels were plated to the same thickness with a commercial bri~h~ nickel electro-deposit and with a commercial bright zinc electrodepos-it. The nickel plated panels and zinc plated pa'nels were then subjected to the standard salt spray test.and it was.determined that exposure for only 8 hours and 40 hours, respectively~ ~as required for red rust to de-velop on the ~Iickel deposit and on the zinc deposit.
The thicknesses of the zinc-nickel alloy elec-trodeposits produced in accordance with Examples 1, 2 and 7 were measured at various distances from the high current 5 ide of the Hull Cell plate. These thicknesses were then plotted against the distance frQm the high current side of the Hu11 Cell plate, as is shown in ~5 Figure 1. These results show that the addition brightening additives of the present inventiondoes not have any significant adverse effect on the thickness of the electrodeposit obtained t over a wide range of current dens ities, as compared to the deposits obtained from a similar electroplating bath which ~oes not con-tain these additives.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An aqueous composition for the electrodeposi-tion of zinc-nickel alloys which comprises at least 10 g/l zinc, at least 15 g/l nickel, at least 20 g/l ammonium ions, a total chloride content of at least 90 grams/litre, and a nonionic polyoxylated surfactant in an amount sufficient to effect grain refinement of the zinc-nickel alloy electro-deposit and make it at least semi-bright, which bath has a weight ratio of nickel-zinc of at least 0.5 and a pH of from about 4.7 to about 8Ø

2. The composition as claimed in claim 1, in which the zinc is present in an amount of from 10 to about 90 g/l, the nickel is present in an amount of from about 15 to about 60 g/l, the ammonium ions are present in an amount of from about 20 to about 120 g/l, the nonionic polyoxylated surfactant is present in an amount from about 0.1 to about 200 g/l, the weight ratio of nickel/zinc is from about 0.5 to about 10 and the pH is from about 5.0 to about 7Ø

3. The composition as claimed in claim 1, wherein there is also present a secondary brightener selected from aromatic aldehydes and aromatic ketones, which secondary brightener is present in an amount sufficient to impart mirror brightness to the zinc-nickel electrodeposit.

4. The composition as claimed in claim 2, wherein there is also present a secondary brightener selected from aromatic aldehydes and aromatic ketones, which secondary brightener is present in an amount from about 0.01 to about 2 g/l.

5. The composition as claimed in Claim 1 wherein there is also present an auxiliary low current density brightener selected from lower alkyl carboxylic acids and their salts, which auxiliary brightener is present in an amount of from about 0.5 to about 25 g/l.

6. The composition as claimed in Claim 2 wherein there is also present an auxiliary low current density brightener selected from lower alkyl carboxylic acids and their salts, which auxiliary brightener is present in an amount of from about 1.0 to about 10 g/l.

7. The composition as claimed in Claim 3 wherein there is also present an auxiliary low current density brightener selected from lower alkyl carboxylic acids and their salts, which auxiliary brightener is present in an amount of from about 0.5 to about 25 g/l.

8. The composition as claimed in Claim 4 wherein there is also present an auxiliary low current density area brightener selected from lower alkyl carboxylic acids and their salts, which auxiliary brightener is present in an amount of from about 1.0 to about 10 g/l.

9. The composition as claimed in Claim 2 wherein the nonionic polyoxyalkylated surfactant is ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol.

10. The composition as claimed in Claim 4 wherein the nonionic polyoxyalkylated surfactant is ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol and the secondary brightener is benzalacetone.

11. The composition as claimed in claim 6, wherein the nonionic polyoxyalkylated surfactant is ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol and the auxiliary low current density area brightener is sodium acetate.

12. The composition as claimed in claim 8, wherein the nonionic polyoxyalkylated surfactant is 2,4,7,9-tetra-methyl-5-decyne-4,7-diol, the secondary brightener is benz-alacetone and the auxiliary low current density area brigh-tener is sodium acetate.

13. A composition as claimed in claim 1, 2 or 3, which has a total chloride content of from about 150 to 300 grams/litre.

14. A process for producing bright, uniform zinc-nickel alloy electrodeposits which comprises passing an electric current through the aqueous composition of claim 1, 3 or 5, between an anode and a cathode, and continuing said passage of said electric current for a period sufficient to effect the deposition of the desired zinc-nickel alloy electrodeposit on the cathode substrate.