Effect of Equal-Channel Angular Pressing on Pitting Corrosion of Pure Aluminum

The effect of equal-channel angular pressing (ECAP) on the pitting corrosion of pure Al was investigated using electrochemical techniques in solutions containing 0.1 m mol.dm(-3) of Na2SO4 and 8.46 mol . dm(-3) of NaCl (300 ppm Cl-) and followed by surface analysis. The potential for pitting corrosion of pure Al was clearly shifted in the noble direction by the ECAP process indicating that this process improves resistance to pitting corrosion. The time dependence of corrosion potential and the anodic potential at 1A.m(-2) revealed that the rate of formation of Al oxide films increased due to a decrease in the grain size of the Al after ECAP. Since there exists a negligible amount of impurity precipitates in pure Al, the improvement in pitting corrosion resistance of pure Al by ECAP appears to be attributable to an increase in the rate of formation of Al oxide films.