Zinc-nickel alloy electroplating system

Abstract

The invention provides an aqueous zinc-nickel alloy electroplating composition particularly useful in an electroplating method for depositing a zinc-nickel alloy layer on a substrate, wherein the deposited layer exhibits uniform nickel concentration and good aesthetics across a broad range of current densities. The electroplating composition comprises an electrolyte composition and an organic composition. In one embodiment, the electrolyte composition comprises a zinc ion source, a nickel ion source, a pH buffering agent and at least one additional salt, and the organic composition comprises a Class I nickel brightener, a Class II nickel brightener, an aromatic carboxylic acid, an aldehyde or ketone compound, and a non-ionic or anionic surfactant. The electroplating composition is particularly free of chelators and free ammonium-producing agents.

1 . An aqueous zinc-nickel alloy electroplating composition comprising an electrolyte composition and an organic composition, wherein the electrolyte composition comprises: 
 a) a zinc ion source;    b) a nickel ion source;    c) a pH buffering agent; and    d) at least one additional inorganic salt;    the organic composition comprises:    a) a Class I nickel brightener;    b) a Class II nickel brightener;    c) an aromatic carboxylic acid;    d) an aldehyde or ketone compound; and    e) a non-ionic or anionic surfactant;    and wherein the electroplating composition is acidic, substantially free from chelating agents, and substantially free from agents producing free ammonium ions in solution.    
   
   
       2 . The electroplating composition of  claim 1 , wherein the composition comprises a zinc ion source selected from the group consisting of zinc chloride, zinc sulfate, zinc acetate, zinc carbonate, zinc sulfamate, and combinations thereof.  
   
   
       3 . The electroplating composition of  claim 1 , wherein the electrolyte composition comprises zinc ions in an amount of about 15 g/L to about 120 g/L.  
   
   
       4 . The electroplating composition of  claim 1 , wherein the composition comprises a nickel ion source selected from the group consisting of nickel chloride, nickel sulfate, nickel acetate, nickel carbonate, nickel sulfamate, and combinations thereof.  
   
   
       5 . The electroplating composition of  claim 1 , wherein the electrolyte composition comprises nickel ions in an amount of about 10 g/L to about 100 g/L.  
   
   
       6 . The electroplating composition of  claim 1 , wherein the composition comprises a pH buffering agent selected from the group consisting of carboxylic acids, salts of carboxylic acids, borates, phosphoric acid, salts of phosphoric acid, and combinations thereof.  
   
   
       7 . The electroplating composition of  claim 6 , wherein the composition comprises a pH buffering agent selected from the group consisting of boric acid, sodium acetate, phosphoric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, and combinations thereof.  
   
   
       8 . The electroplating composition of  claim 1 , wherein the pH buffering agent provides buffering at a pH range of about 2 to about 7.  
   
   
       9 . The electroplating composition of  claim 1 , wherein the pH buffering agent is present at a concentration of about 20 g/L to about 60 g/L.  
   
   
       10 . The electroplating composition of  claim 1 , wherein the at least one additional inorganic salt is selected from the group consisting of chloride salts, sulfate salts, and combinations thereof.  
   
   
       11 . The electroplating composition of  claim 1 , wherein the at least one additional inorganic salt is selected from the group consisting of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, sodium acetate, methansulfonic acid, sulfamic acid, and combinations thereof.  
   
   
       12 . The electroplating composition of  claim 1 , wherein the at least one additional inorganic salt is present at a concentration of about 50 g/L to about 500 g/L.  
   
   
       13 . The electroplating composition of  claim 1 , wherein the electrolyte component comprises zinc chloride, nickel chloride hexahydrate, boric acid, sodium acetate, and potassium chloride.  
   
   
       14 . The electroplating composition of  claim 1 , wherein the composition comprises one or more Class I nickel brightener selected from the group consisting of alkyl naphthalenes, benzene sulfonic acids, benzene disulfonic acids, benzene trisulfonic acids, naphthalene disulfonic acids, naphthalene trisulfonic acids, benzene sulfonamides, naphthalene sulfonamides, benzene sulfonamides, naphthalene sulfonimides, vinyl sulfonamides, allyl sulfonamides, salts thereof, and combinations thereof.  
   
   
       15 . The electroplating composition of  claim 1 , wherein the composition comprises one or more Class I nickel brightener selected from the group consisting of saccharin, saccharin salts, bis-benzenesulfonylimide, carboxyethyl isothiuronium betaine, 2-thiohydantoin, trisodium 1,3,6-naphthalene trisulfonic acid, trisodium 1,3,7-naphthalene trisulfonic acid, benzene sulfinic acid, sodium styrene sulfonate, p-toluene sulfinic acid, p-toluene sulfonic acid, ditolylsulfimide, sodium salt of di-o-tolyl disulfimide, sodium salt of dibenzene disulfimide, pyridine-3-sulfonic acid, p-vinylbenzene sulfonic acid, sodium allyl sulfonate, sodium vinyl sulfonate, sodium propargyl sulfonate, sodium benzene monosulfonate, dibenzene sulfonamide, sodium benzene monosulfinate, sodium-3-chloro-2-butene-1-sulfonate, sodium β-styrene sulfonate, monoallyl sulfamide, diallyl sulfamide, sodium propyne sulfonate, sodium allyl sulfonate, allyl sulfonamide, and combinations thereof.  
   
   
       16 . The electroplating composition of  claim 1 , wherein the Class I nickel brightener is present at a concentration of about 0.1 g/L to about 5 g/L.  
   
   
       17 . The electroplating composition of  claim 1 , wherein the composition comprises one or more Class II nickel brightener selected from the group consisting of derivatives of acetylenic alcohols, derivatives of acetylenic amines, derivatives of ethylenic alcohols, derivatives of ethylenic amines, reaction products of epoxides with acetylenic or ethylenic alcohols or amines, N-heterocyclics, ethoxylated acetylenic alcohols, propoxylated acetylenic alcohols, coumarins, compounds containing a C≡N group, and combinations thereof.  
   
   
       18 . The electroplating composition of  claim 1 , wherein the composition comprises one or more Class II nickel brightener selected from the group consisting of dipropoxylated 2-butyne-1,4-diol, 1,4-di-(β-hydroxyethoxy)-2-butyne, 1,4-di-(β-hydroxy-γ-chloropropoxy)-2-butyne, 1,4-di-(β-γ-epoxypropoxy)-2-butyne, 1,4-di-(2′-hydroxy-4′-oxa-6′-heptenoxy)-2-butyne, N-1,2-dichloropropenyl pyridinium chloride, 2,4,6-trimethyl N-propargyl pyridinium bromide, N-allyl quinaldinium bromide, N-allyl quinolinium bromide, 2-butyne-1,4-diol, propargyl alcohol, N,N-diethyl-2-propyne-amine, dimethyldiallylammonium chloride, pyridinium-propyl-sulfobetaine, 2-methyl-3-butyn-2-ol, thiodiproprionitrile, hydroxyethyl propynyl ether, β-hydroxypropyl propynyl ether, bis-(β-hydroxypropyl ether)-2-butyn-1,4-diol, γ-propynoxy propyl sulfonic acid, γ-propynoxy-β-hydroxypropyl sulfonic acid, 1-(γ-sulfopropoxy)-2-butyn-4-ol, 1,4-di-(β-hydroxy-γ-sulfonic propoxy)-2-butyne, derivatives thereof, and combinations thereof.  
   
   
       19 . The electroplating composition of  claim 1 , wherein the Class II nickel brightener is present at a concentration of about 0.05 g/L to about 3 g/L.  
   
   
       20 . The electroplating composition of  claim 1 , wherein the composition comprises one or more aromatic carboxylic acid selected from the group consisting of benzoic acid, sodium benzoate, salicylic acid, sodium salicylate, niacin, niacinamide, cinnamic acid, phenyl propiolic acid, benzoyl acetic acid, o-coumaric acid, benzoyl acetic acid ethyl ester, and combinations thereof.  
   
   
       21 . The electroplating composition of  claim 1 , wherein the aromatic carboxylic acid is present at a concentration of about 0.01 g/L to about 3 g/L.  
   
   
       22 . The electroplating composition of  claim 1 , wherein the composition comprises one ore more aldehyde or ketone compound useful as a top brightener in a zinc electroplating system.  
   
   
       23 . The electroplating composition of  claim 1 , wherein the composition comprises one or more aldehyde or ketone compound selected from the group consisting of aryl aldehydes, aryl ketones, ring-halogenated aryl aldehydes, ring-halogenated aryl ketones, heterocyclic aldehydes, heterocyclic ketones, aryl olefinic aldehydes, aryl olefinic ketones, aryl olefinic lactone, carbocyclic olefinic aldehydes, carbocyclic olefinic ketones, and combinations thereof.  
   
   
       24 . The electroplating composition of  claim 1 , wherein the composition comprises one or more aldehyde or ketone compound selected from the group consisting of o-anisic aldehyde, p-anisic aldehyde, o-chlorobenzaldehyde, p-chlorobenzaldehyde, cinnaldehyde, piperonal, benzylidene acetone, 2,4-dichlorobenzaldehyde, 2,6-dichlorobenzaldehyde, 2-hydroxy-1-naphthaldehyde, furfuryl acetone, thiophene aldehyde, benzal acetone, β-ionone, and combinations thereof.  
   
   
       25 . The electroplating composition of  claim 1 , wherein the aldehyde or ketone compound is present at a concentration of about 1 mg/L to about 100 mg/L.  
   
   
       26 . The electroplating composition of  claim 1 , wherein the composition comprises two or more aldehyde or ketone compounds.  
   
   
       27 . The electroplating composition of  claim 1 , wherein the composition comprises one or more non-ionic surfactant selected from the group consisting of homopolymers of ethylene oxide, homopolymers of propylene oxide, propylene oxide-ethylene oxide block copolymers, ethylene oxide condensation products of naphthol and long chain fatty alcohols, ethylene oxide condensation products of naphthol and long chain fatty amines, ethylene oxide condensation products of naphthol and long chain fatty acids, ethylene oxide condensation products of naphthol and long chain alkyl phenol, alkoxylated alkyl phenols, alkyl naphthols, aliphatic monohydric alcohols, aliphatic polyhydric alcohols, oxo alcohol ethoxylates, alkylphenol ethoxylates, fatty alcohol ethoxylates, β-naphthol ethoxylates, and combinations thereof.  
   
   
       28 . The electroplating composition of  claim 1 , wherein the composition comprises one or more anionic surfactant selected from the group consisting sodium dialkylsulfosuccinates, sulfonated or sulfated alkylalkoxylates, alkylphenol sulfonates or sulfates, naphthalenesulfonic acids, and combinations thereof.  
   
   
       29 . The electroplating composition of  claim 1 , wherein the non-ionic or anionic surfactant is present at a concentration of about 0.05 g/L to about 10 g/L.  
   
   
       30 . The electroplating composition of  claim 1 , wherein the composition comprises a non-ionic surfactant and an anionic surfactant.  
   
   
       31 . The electroplating composition of  claim 1 , further comprising one or more hydrotrope compounds.  
   
   
       32 . The electroplating composition of  claim 1 , wherein the one or more hydrotrope compounds comprises sodium cumene sulfate.  
   
   
       33 . The electroplating composition of  claim 1 , wherein the composition is prepared batchwise combining the components of the electrolyte composition and the components of the organic composition at the time of use.  
   
   
       34 . The electroplating composition of  claim 1 , wherein the electrolyte composition and the organic composition are prepared as separate compositions and predetermined volumes of the electrolyte composition and the organic composition are combined at the time of use to form the electroplating composition.  
   
   
       35 . The electroplating composition of  claim 1 , wherein the electrolyte composition is prepared prior to a time of use and the components of the organic composition are added to the electrolyte composition at the time of use to prepare said electroplating composition.  
   
   
       36 . The electroplating composition of  claim 1 , wherein the electroplating composition is completely free from chelating agents.  
   
   
       37 . The electroplating composition of  claim 1 , wherein the electroplating composition is completely free from agents producing free ammonium ions in solution.  
   
   
       38 . A method for depositing a zinc-nickel alloy on a substrate, the method comprising immersing the substrate in an aqueous electroplating composition comprising an electrolyte composition and an organic composition, wherein the electrolyte composition comprises: 
 a) a zinc ion source;    b) a nickel ion source;    c) a pH buffering agent; and    d) at least one additional salt;    the organic composition comprises:    a) a Class I nickel brightener;    b) a Class II nickel brightener;    c) an aromatic carboxylic acid;    d) an aldehyde or ketone compound; and    e) a non-ionic or anionic surfactant;    and wherein the electroplating composition is acidic, substantially free from chelating agents, and substantially free from agents producing free ammonium ions in solution; and    applying an electrical current to the immersed substrate for a time sufficient to deposit a layer of a zinc-nickel alloy on the substrate.    
   
   
       39 . The method of  claim 38 , wherein the zinc-nickel alloy layer deposited on the substrate comprises an average nickel concentration in a range of about 5% to about 15%, based on the overall weight of the deposition layer, when the zinc-nickel alloy layer is deposited at a current density of about 2 ASF to about 50 ASF.  
   
   
       40 . The method of  claim 38 , wherein the zinc-nickel alloy layer deposited on the substrate comprises an average nickel concentration in a range of about 5% to about 15%, based on the overall weight of the deposition layer, when the zinc-nickel alloy layer is deposited at a current density of about 0.5 ASF to about 120 ASF.  
   
   
       41 . The method of  claim 38 , wherein the zinc-nickel alloy layer is deposited such that the average nickel concentration varies from a highest concentration to a lowest concentration by less than about 3 percentage points when the zinc-nickel alloy layer is deposited at a current density of about 2 ASF to about 50 ASF.  
   
   
       42 . The method of  claim 38 , wherein said electroplating composition during said method is within a temperature range of about 85° F. to about 120° F.  
   
   
       43 . The method of  claim 38 , wherein the electrolyte composition comprises zinc ions in an amount of about 15 g/L to about 120 g/L.  
   
   
       44 . The method of  claim 38 , wherein the electrolyte composition comprises nickel ions in an amount of about 10 g/L to about 100 g/L.  
   
   
       45 . The method of  claim 38 , wherein the pH buffering agent provides buffering at a pH range of about 2 to about 7.  
   
   
       46 . The method of  claim 38 , wherein the pH buffering agent is present at a concentration of about 20 g/L to about 60 g/L.  
   
   
       47 . The method of  claim 38 , wherein the at least one additional inorganic salt is present at a concentration of about 50 g/L to about 500 g/L.  
   
   
       48 . The method of  claim 38 , wherein the Class I nickel brightener is present at a concentration of about 0.1 g/L to about 5 g/L.  
   
   
       49 . The method of  claim 38 , wherein the Class II nickel brightener is present at a concentration of about 0.05 g/L to about 3 g/L.  
   
   
       50 . The method of  claim 38 , wherein the aromatic carboxylic acid is present at a concentration of about 0.01 g/L to about 3 g/L.  
   
   
       51 . The method of  claim 38 , wherein the aldehyde or ketone compound is present at a concentration of about 1 mg/L to about 100 mg/L.  
   
   
       52 . The method of  claim 38 , wherein the organic composition includes two or more aldehyde or ketone compounds.  
   
   
       53 . The method of  claim 38 , wherein the non-ionic or anionic surfactant is present at a concentration of about 0.05 g/L to about 10 g/L.  
   
   
       54 . The method of  claim 38 , wherein the organic composition includes a non-ionic surfactant and an anionic surfactant.  
   
   
       55 . The method of  claim 38 , wherein the organic composition further comprises one or more hydrotrope compounds.  
   
   
       56 . The method of  claim 38 , wherein said electroplating composition is prepared batchwise combining the components of the electrolyte composition and the components of the organic composition at the time of carrying out said method.  
   
   
       57 . The method of  claim 38 , wherein said electrolyte composition and said organic composition are prepared as separate compositions and specified volumes of the electrolyte composition and the organic composition are combined to form said electroplating composition at the time of carrying out said method.  
   
   
       58 . The method of  claim 38 , wherein said electrolyte composition is prepared prior to carrying out said method and the components of the organic composition are added to said electrolyte composition at the time of carrying out said method to prepare said electroplating composition.