Surface treatment method for housing

Abstract

A surface treatment method for housings comprising: providing a metal housing and pre-treating it to be cleaned; electroplating the housing to form a hexavalent chromium coating on the surface of the housing; and electroplating the housing to form a trivalent chromium coating on the hexavalent chromium coating.

1 . A surface treatment method for housings, comprising:
 providing a metal housing and pre-treating it to be cleaned;   electroplating the housing to form a hexavalent chromium coating on a surface of the housing; and   electroplating the housing to form a trivalent chromium coating on the hexavalent chromium coating.   
   
   
       2 . The surface treatment method as claimed in  claim 1 , wherein the metal housing is made of stainless steel or copper. 
   
   
       3 . The surface treatment method as claimed in  claim 1 , wherein electroplating the housing to form the hexavalent chromium coating is carried out in a second electrolyte containing a chromium acid component in a mass concentration of about 240-350 g/L and a sulfuric acid component in a mass concentration of about 2-4 g/L. 
   
   
       4 . The surface treatment method as claimed in  claim 3 , wherein the second electrolyte further contains fluoride additive agent(s) in a mass concentration of about 5-10 g/L. 
   
   
       5 . The surface treatment method as claimed in  claim 4 , wherein the electric current density through the second electrolyte is about 10-30 A/dm 2 , and the electroplating last for about 1-15 minutes. 
   
   
       6 . The surface treatment method as claimed in  claim 1 , wherein electroplating the housing to form the trivalent chromium coating is carried out in a third electrolyte containing a chromium sulphate component and a boric acid component, the mass concentration of the trivalent chromium iron in the third electrolyte is about 3-10 g/L. 
   
   
       7 . The surface treatment method as claimed in  claim 6 , wherein the electric current density through the third electrolyte is about 5-15 A/dm 2 , and the electroplating last for about 1-15 minutes. 
   
   
       8 . The surface treatment method as claimed in  claim 1 , wherein the housing is subjected to neutralization treatment after the electroplating process in a neutralization solution including a sulfuric acid component and an oxydol component. 
   
   
       9 . The surface treatment method as claimed in  claim 1 , wherein pre-treating the housing includes degreasing, electrochemical cleaning and acid treating the housing. 
   
   
       10 . The surface treatment method as claimed in  claim 9 , wherein electrochemical cleaning the housing is carried out in a first electrolyte containing a sodium hydroxide component, the temperature of the first electrolyte is about 55-65° C., the electric current density through the first electrolyte is about 1-5 A/dm 2 , and the electrochemical cleaning last for about 4-10 minutes.