Anodization treatment method for aluminum alloys containing cooper

Abstract

A method of treating a part made of an aluminum alloy containing copper at a content in the range 0.1% to 10% by weight includes providing the part; and performing electrochemical pretreatment of the part in a first electrolyte bath containing sulfuric acid and a first oxidizer compound, a first potential difference being established between a first cathode and a first anode dipped in the first bath, the part being the first anode, the concentration of the first oxidizer compound being such that the corrosion potential of the aluminum alloy is greater than +100 mV relative to a hydrogen normal electrode. After the pretreatment, the method includes anodizing the part in a second electrolyte bath containing sulfuric acid and a second oxidizer compound, a second potential difference □V2 being established between a second cathode and a second anode dipped in the second bath, the part being the second anode.

What is claimed is: 
     
         1 . A method of treating a part made of aluminum alloy containing copper at a content lying in the range 0.1% to 10% by weight, wherein the method comprises:
 a. providing said part;   b. performing electrochemical pretreatment of said part in a first electrolyte bath containing sulfuric acid and a first oxidizer compound, a first potential difference ΔV 1  being established between a first cathode and a first anode dipped in said first bath, said part being said first anode, the concentration of said first oxidizer compound being such that the corrosion potential of said aluminum alloy is greater than +100 mV relative to a hydrogen normal electrode;   c. after step b, anodizing said part in a second electrolyte bath containing sulfuric acid and a second oxidizer compound, a second potential difference ΔV 2  being established between a second cathode and a second anode dipped in said second bath, said part being said second anode.   
     
     
         2 . A method according to  claim 1 , wherein, in step b, said first potential difference ΔV 1  lies in the range 3 V to 12 V. 
     
     
         3 . A method according to  claim 1 , wherein said first oxidizer compound is hydrogen peroxide H 2 O 2 . 
     
     
         4 . A method according to  claim 1 , wherein anodizing step c is performed in the same bath as the first bath of the pretreatment step b, without extracting said part from said first bath between step b and step c. 
     
     
         5 . A method according to  claim 1 , wherein between step b and step c, a step is performed of rinsing said part. 
     
     
         6 . A method according to  claim 5 , wherein said rinsing is constituted by:
 b1. rinsing said part in a static rinsing bath; and   b2. then rinsing said part in a running rinsing bath with softened water.