White trivalent chromium plating bath and white trivalent chromium plating method for object to be plated using same

Abstract

A white trivalent chromium plating bath including a trivalent chromium compound, a complexing agent, a sulfate serving as a conductive salt, a pH buffering agent, and one type or two or more types of sulfur-containing organic compounds represented by the following general formula (I) (in which R represents —H, —NH2, —OH, —CH3, —(CH2)n—CH3, or —(CH2)n—COOH, n represents an integer of 1 to 4, and X and Y each independently represent CH2, C═O, or C═S), and a white trivalent chromium plating method using the white trivalent chromium plating bath enable a high plating deposition rate in the trivalent chromium plating bath, and provide an appearance suitable for decorative applications.

1 . A white trivalent chromium plating bath comprising:
 a trivalent chromium compound;   a complexing agent;   a sulfate serving as a conductive salt;   a pH buffering agent; and   a sulfur-containing organic compound represented by the following formula (I):   
       
         
           
           
               
               
           
         
         wherein R represents —H, —NH 2 , —OH, —CH 3 , —(CH 2 ) n —CH 3 , or —(CH 2 )—COOH, n represents an integer of 1 to 4, and X and Y each independently represent CH 2 , C═O, or C═S. 
       
     
     
         2 . A white trivalent chromium plating bath comprising:
 a trivalent chromium compound;   a complexing agent;   a sulfate serving as a conductive salt;   a pH buffering agent; and   a sulfur-containing organic compound represented by the following formula (II):   
       
         
           
           
               
               
           
         
         wherein R represents —H, —NH 2 , —OH, —CH 3 , —(CH 2 ) n —CH 3 , or —(CH 2 ) n —COOH, n represents an integer of 1 to 4, and X 1  and Y 1  each independently represent C═O or C═S. 
       
     
     
         3 . The white trivalent chromium plating bath according to  claim 1 , wherein the complexing agent is a dicarboxylic acid or a salt thereof. 
     
     
         4 . The white trivalent chromium plating bath according to  claim 3 , wherein the dicarboxylic acid is malic acid and/or tartaric acid. 
     
     
         5 . The white trivalent chromium plating bath according to  claim 1 , further comprising saccharin or a salt thereof. 
     
     
         6 . A white trivalent chromium plating method for an object to be plated, the method comprising:
 electroplating the object to be plated in the white trivalent chromium plating bath according to  claim 1 .   
     
     
         7 . A method for improving a deposition rate of white trivalent chromium plating, the method comprising:
 incorporating a sulfur-containing organic compound represented by the following formula (I):   
       
         
           
           
               
               
           
         
         wherein R represents —H, —NH 2 , —OH, —CH 3 , —(CH 2 ) n —CH 3 , or —(CH 2 ) n —COOH, n represents an integer of 1 to 4, and X and Y each independently represent CH 2 , C═O, or C═S in a white trivalent chromium plating bath containing 
         a trivalent chromium compound; 
         a complexing agent; 
         a sulfate serving as a conductive salt; and 
         a pH buffering agent.