Pitting Corrosion Resistance of Anodized Aluminum-Copper Alloy Processed by Severe Plastic Deformation

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L of AlCl3 and also by surface analysis. The time required before initiating pitting corrosion of anodized Al-CU alloy was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. Second phase precipitates were present in Al-CU alloy matrix and the size of these precipitates was greatly decreased by application of ECAP. The precipitates composed of Si and Al-Cu-Si-Fe-Mn were not oxidized during anodization, and the anodic oxide film were absent at the boundary between the normal oxide films and these impurity precipitates. The pitting corrosion of anodized Al-Cu alloy occurred preferentially around these precipitates, the improvement of pitting corrosion resistance of anodized Al-Cu alloy by ECAP appears to be attributable to a decrease in the size of precipitates, which act as origins of pitting corrosion. [doi: 10.2320/matertrans.MRA2008216]