Nickel electroplating bath designed to replace monovalent copper strike solutions

Abstract

A nickel electroplating bath is disclosed which is suitable for plating, a base layer of nickel over zinc or zinc alloy parts. Subsequent plating onto this base layer can be achieved with copper, chromium or bright nickel with good adhesion and appearance. The nickel electroplating solution proposed comprises an additive package comprising (i) sulphonic acid or sulphonic acid salts, (ii) sulfonated alkoxylate and (iii) organic acid selected from the group consisting of tolylacetic acid, salicylic acid, hydroxy-benzoic acid, benzyloxyacetone and mixtures of the foregoing.

1 . A method of electroplating nickel directly onto zinc or zinc alloys, said method comprising contacting the zinc or zinc alloy with a nickel electroplating bath comprising: 
 a) nickel ions;    b) counter ions;    c) chloride ions;    d) buffer selected from the group consisting of boric acid, mono-carboxylic acids, di-carboxylic acids, tri-carboxylic acids and salts of any of the foregoing materials;    e) sulphonic acids or sulphonic acid salts;    f) sulfonated alkoxylate; and    g) organic compound selected from the group consisting of tolylacetic acid, salicylic acid, hydroxybenzoic acid, benzoic acid, benzyloxyacatone, salicylic acid and mixtures of the foregoing.    
   
   
       2 . A method according to  claim 1 , wherein the zinc and zinc alloy is subsequently plated with copper, chromium, bright nickel or brass.  
   
   
       3 . A method according to  claim 1 , wherein the nickel electroplating bath also comprises at least one additive selected from the group consisting of surfactants, water-soluble polymers, glycerol, glycerol derivatives, and mixtures of the foregoing.  
   
   
       4 . A method according to  claim 1 , wherein the concentration of nickel ions is from 10 g/l to 100 g/l, the concentration of the buffer is from 5 g/l to 70 g/l, the concentration of sulphonic acid or sulphonic acid salt is from 0.2 g/l to 5 g/l, the concentration of sulfonated alkoxylate is from 0.1 to 1.5 g/l and the concentration of the organic compound is from 0.1 g/l to 25 g/l.  
   
   
       5 . A method according to  claim 1 , wherein the buffer is selected from the group consisting of boric acid, acetic acid, malic acid, succinic acid, citric acid and salts of the foregoing.  
   
   
       6 . A method according to  claim 1 , wherein the pH of the nickel electroplating bath is between 5 and 6.  
   
   
       7 . A method according to  claim 1 , wherein an average current density of 0.5 to 10 A/dm 2  is applied to the zinc or zinc alloy in the nickel electroplating bath.  
   
   
       8 . A nickel electroplating bath comprising: 
 a) nickel ions;    b) counter ions;    c) chloride ions;    d) buffer selected from the group consisting of boric acid, mono-carboxylic acids, di-carboxylic acids, tri-carboxylic acids and salts of any of the foregoing materials;    e) sulphonic acid or sulphonic acid salts;    f) sulfonated alkoxylate; and    g) organic compound selected from the group consisting of tolylacetic acid, salicylic acid, hydroxybenzoic acid, benzoic acid, benzyloxyacatone, salicylic acid and mixtures of the foregoing.    
   
   
       9 . A bath to  claim 1 , wherein the nickel electroplating bath also comprises at least one additive selected from the group consisting of surfactants, water-soluble polymers, glycerol, glycerol derivatives, and mixtures of the foregoing.  
   
   
       10 . A bath according to  claim 1 , wherein the concentration of nickel ions is from 10 g/l to 100 g/l, the concentration of the buffer is from 5 g/l to 70 g/l, the concentration of sulphonic acid or sulphonic acid salt is from 0.2 g/l to 5 g/l, the concentration of sulfonated alkoxylate is from 0.1 to 1.5 g/l and the concentration of the organic compound is from 0.1 g/l to 25 g/l.  
   
   
       11 . A bath according to  claim 1 , wherein the buffer is selected from the group consisting of boric acid, acetic acid, malic acid, succinic acid, citric acid and salts of the foregoing.  
   
   
       12 . A bath according to  claim 1 , wherein the pH of the nickel electroplating bath is between 5 and 6.