Process for treating the surface of a part made of aluminium or aluminium alloy or of magnesium or magnesium alloy

Abstract

The invention relates to a method for the surface treatment of a part made from aluminum or aluminum alloy or from magnesium or magnesium alloy, comprising a step of treatment by oxidation of said part and a step of applying an aqueous composition to the surface of said part.

1 . A method for the surface treatment of a part made from aluminum or aluminum alloy or from magnesium or magnesium alloy, the method comprising:
 oxidation treating said part; and,   applying, to the surface of said part, an aqueous composition free of chromium, the aqueous composition containing:
 fluorozirconate ions, 
 molybdate ions, 
 and at least one component selected from lithium ions and permanganate ions. 
   
     
     
         2 . The method according to  claim 1 , wherein said oxidation treatment of said part is an anodization treatment. 
     
     
         3 . The method according to  claim 1  wherein said oxidation treatment of said part is a micro-arc oxidation. 
     
     
         4 . The method according to  claim 1  wherein said application is carried out by immersing said part in a bath of said aqueous composition. 
     
     
         5 . The method according to  claim 1  wherein said aqueous composition applied during the application has a temperature of between 10 and 60° C. 
     
     
         6 . The method according to  claim 1  wherein said application is carried out for a time greater than or equal to 5 minutes, preferably between 5 and 20 minutes. 
     
     
         7 . The method according to  claim 1  further comprising preliminarily pretreating said part by at least one of chemical degreasing and pickling. 
     
     
         8 . The method according to  claim 1  wherein said aqueous composition contains lithium ions and permanganate ions. 
     
     
         9 . The method according to  claim 1  wherein said aqueous composition contains cerium ions. 
     
     
         10 . The method according to  claim 1  wherein said aqueous composition contains nitrate ions. 
     
     
         11 . The method according to  claim 10 , wherein said aqueous composition contains lithium nitrate. 
     
     
         12 . The method according to  claim 1  wherein said aqueous composition has a pH of between 3 and 7. 
     
     
         13 . The method according to  claim 1  wherein said aqueous composition contains at least one of the following concentrations:
 between 5 and 30 g/l of fluorozirconate salt, 
 between 2.5 and 10 g/l of molybdate salt, 
 between 2 and 8 g/l of lithium salt, 
 between 4 and 19 g/l of permanganate salt, 
 and/or between 0.1 and 0.5 g/l of cerium salt. 
 
     
     
         14 . A part made from aluminum or aluminum alloy or from magnesium or magnesium alloy obtained by a surface treatment comprising:
 oxidation treating said part; and,   applying, to the surface of said part, an aqueous composition free of chromium, the aqueous composition containing:   fluorozirconate ions,   molybdate ions,   and at least one component selected from lithium ions and   permanganate ions.