Zinc plating bath additive and alkaline non-cyanide zinc plating bath

Abstract

Provided is a zinc plating bath additive enabling the rapid formation of a zinc coating having small variations in the thickness depending on the position on the surface of an object to be plated. The zinc plating bath additive contains a water soluble copolymer having, as the structural units, two amine compounds.

1 - 12 . (canceled) 
     
     
         13 . A zinc plating bath additive comprising a water soluble copolymer having structural units (a) each represented by the following formula (1) and structural units (b) each represented by the following formula (2): 
       
         
           
           
               
               
           
         
       
     
     
         14 . The zinc plating bath additive according to  claim 13 , wherein the structural units (a) and the structural units (b) are contained in the water soluble copolymer so that a percentage of the mass of the structural units (a) relative to the sum of the mass of the structural units (a) and the mass of the structural units (b) is from 10 to 60%. 
     
     
         15 . The zinc plating bath additive according to  claim 13 , wherein in the water soluble copolymer, the structural units (a), the structural units (b), or the structural unit (a) and the structural unit (b) have been linked to each other via a linking group represented by the following formula (3) and/or the following formula (4): 
       
         
           
           
               
               
           
         
         (in the formula (3), a stands for an integer from 1 to 5, b stands for an integer from 1 to 5, d stands for an integer from 1 to 5, e stands for an integer from 1 to 5, and m stands for an integer from 0 to 5, while in the formula (4), f stands for an integer from 1 to 5, g stands for an integer from 1 to 5, h stands for an integer from 1 to 5, i stands for an integer from 1 to 5, and n stands for an integer from 0 to 5). 
       
     
     
         16 . The zinc plating bath additive according to  claim 14 , wherein in the water soluble copolymer, the structural units (a), the structural units (b), or the structural unit (a) and the structural unit (b) have been linked to each other via a linking group represented by the following formula (3) and/or the following formula (4): 
       
         
           
           
               
               
           
         
         (in the formula (3), a stands for an integer from 1 to 5, b stands for an integer from 1 to 5, d stands for an integer from 1 to 5, e stands for an integer from 1 to 5, and m stands for an integer from 0 to 5, while in the formula (4), f stands for an integer from 1 to 5, g stands for an integer from 1 to 5, h stands for an integer from 1 to 5, i stands for an integer from 1 to 5, and n stands for an integer from 0 to 5). 
       
     
     
         17 . An alkaline non-cyanide zinc plating bath comprising the zinc plating bath additive as claimed in  claim 13 , zinc ions, and hydroxide ions. 
     
     
         18 . An alkaline non-cyanide zinc plating bath comprising the zinc plating bath additive as claimed in  claim 14 , zinc ions, and hydroxide ions. 
     
     
         19 . An alkaline non-cyanide zinc plating bath comprising the zinc plating bath additive as claimed in  claim 15 , zinc ions, and hydroxide ions. 
     
     
         20 . An alkaline non-cyanide zinc plating bath comprising the zinc plating bath additive as claimed in  claim 16 , zinc ions, and hydroxide ions. 
     
     
         21 . The alkaline non-cyanide zinc plating bath according to  claim 17 , wherein the water soluble copolymer is contained in an amount of from 0.1 to 50 g/L. 
     
     
         22 . The alkaline non-cyanide zinc plating bath according to  claim 17 , comprising N-benzylpyrimidium-3-carbonate. 
     
     
         23 . The alkaline non-cyanide zinc plating bath according to  claim 17 , comprising a bisulfite adduct obtained by adding a bisulfite to the aldehyde group of an aromatic aldehyde compound represented by the following formula (5): 
       
         
           
           
               
               
           
         
         (in the formula (5), R 1 , R 2 , R 3  each represents —H, —OH, or —OCH 3  and R 1  to R 3  may be the same or different). 
       
     
     
         24 . The alkaline non-cyanide zinc plating bath according to  claim 23 , wherein the aromatic aldehyde compound is at least one compound selected from the group consisting of 4-methoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 3,4-dimethoxybenzaldehyde, 3,4-methylenedioxybenzaldehyde, 2-hydroxybenzaldehyde, and 4-hydroxybenzaldehyde. 
     
     
         25 . The alkaline non-cyanide zinc plating bath according to  claim 23 , wherein the bisulfite adduct is contained in an amount of from 0.005 to 1.0 g/L. 
     
     
         26 . The alkaline non-cyanide zinc plating bath according to  claim 17 , wherein the zinc ions are contained in an amount of from 5 to 25 g/L. 
     
     
         27 . The alkaline non-cyanide zinc plating bath according to  claim 17 , comprising at least one compound selected from the group consisting of silicon compounds, sodium ethylenediaminetetraacetate, and trisodium hydroxyethylenediaminetriacetate. 
     
     
         28 . The alkaline non-cyanide zinc plating bath according to  claim 17 , comprising a heterocyclic compound represented by the following formula (6) and/or a derivative of the heterocyclic compound: 
       
         
           
           
               
               
           
         
         (in the formula (6), p stands for an integer from 1 to 3 and R 4  and R 5  may be the same or different and each represents —H, —CH 2 COOH, —CH 2 CH 2 OH, or —CH 2 CH(OH)CH 2 Cl).