Additive for chromium electrolytes

Abstract

The fluorine surfactant-free, long-term-stable and biodegradable additive for chromium electrolytes lowers the surface tension and hence improves the chromium deposition process, especially in the application for the electrolytical chromium-plating. Preferred additives are CH 3 (CH 2 ) n SO 3 H and the salts thereof with n from 10 to 18. These additives are also useful as component in polymer mordants as pretreatments for polymer metallizations.

1 - 7 . (canceled) 
     
     
         8 . A method for electrochemical chromium plating, wherein the method comprises adding an additive to a chromic acid solution used in the electrochemical chromium plating process, wherein the additive:
 (a) comprises at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 10 to 18;   (b) is free of fluorine surfactants;   (c) is biodegradable;   (d) when added to the chromic acid solution results in the chromic acid solution having a surface tension of ≦30 mN/m; and   (e) has a stability of ≧4 h in the chromic acid solution when used in an electrolytical chromium plating process, determined at 45° C. and 6000 Ah of charge passage.   
     
     
         9 . The method of  claim 8 , wherein the additive is present in the chromic acid solution used in the electrolytical chromium-plating process, and the chromic acid solution has a current density of 35 A/dm 2  to 60 A/dm 2 . 
     
     
         10 . The method of  claim 8 , wherein the additive comprises at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 12 to 17. 
     
     
         11 . The method of  claim 8 , wherein the additive comprises at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 14 to 16. 
     
     
         12 . The method of  claim 8 , wherein the additive consists of at least one surfactant having the formula CH 3 (CH 2 ) n ,SO 3 H or a salt thereof, where n is 10 to 18. 
     
     
         13 . The method of  claim 8 , wherein the concentration of the additive is between about 0.05 g/l and about 20 g/l. 
     
     
         14 . The method of  claim 8 , wherein the concentration of the additive is between about 0.05 g/l and about 3 g/l. 
     
     
         15 . A method for pretreating polymer metallization, wherein the method comprises adding an additive to polymer mordant composition used in the pretreatment process, wherein the additive:
 (a) comprises at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 10 to 18;   (b) is free of fluorine surfactants; and   (c) is biodegradable.   
     
     
         16 . The method of  claim 15 , wherein the additive comprises at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 12 to 17. 
     
     
         17 . The method of  claim 15 , wherein the additive comprises at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 14 to 16. 
     
     
         18 . The method of  claim 15 , wherein the additive consists of at least one surfactant having the formula CH 3 (CH 2 ) n SO 3 H or a salt thereof, where n is 10 to 18. 
     
     
         19 . The method of  claim 15 , wherein the concentration of the additive is between about 0.05 g/l and about 20 g/l. 
     
     
         20 . The method of  claim 15 , wherein the concentration of the additive is between about 0.05 g/l and about 3 g/l.