日本金属学会誌

J. Japan Inst. Metals, Vol. 70, No. 7 (2006),
pp. 534-540

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

In-Joon Son1,, Hiroaki Nakano2, Satoshi Oue2, Shigeo Kobayashi3, Hisaaki Fukushima2 and Zenji Horita2

1Department of Materials Process Engineering, Kyushu University, Fukuoka 819-0395
2Department of Materials Science & Engineering, Kyushu University, Fukuoka 819-0395
3Department of Applied Chemistry and Biochemistry, Kyushu Sangyo University, Fukuoka 813-8503

Abstract:

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of anodized Al and Al-Mg alloy was investigated by electrochemical techniques in a solution containing 0.25 mol/L of AlCl3 and by surface analysis. The time required before initiating pitting corrosion of anodized Al was longer with ECAP than without, indicating improvement in the pitting corrosion resistance by application of ECAP. However, in anodized Al-Mg alloy, the pitting corrosion occurred earlier with ECAP than without, showing that the corrosion resistance was worse with ECAP than without. SEM and EPMA observation revealed that pitting corrosion of anodized Al occurred around the impurity precipitates and that the size of the impurity precipitate decreased as a result of the ECAP. The improvement in pitting corrosion resistance of anodized Al by ECAP appears to be attributable to a decrease in the size of impurity precipitates. On the other hand, in anodized Al-Mg alloy, cracks occurred in the anodic oxide films during initial corrosion and the cracks were larger with ECAP than without. It is assumed that the pitting corrosion was promoted by the cracks resulted from ECAP.


(Received 2006/2/6)

Keywords:

aluminum, aluminum-magnesium alloy, equal-channel angular pressing, anodizing, pitting corrosion


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