Effects of cold rolling on corrosion rate of pure aluminum in alkaline solution

The corrosion rate of 99.99mass% aluminum cold-rolled by a constant reduction rate (10% per pass) or a constant reduction amount (10% of original thickness per pass)method were measured in a 0.5mol/l-NaOH solution at 40°C. The changes in corrosion rate with the total reduction 0-90% corresponded very well to the changes in residual stress of the samples. For the sheets rolled by the constant rate method, the corrosion rate and the residual stress showed the maxima at 30% and 80%, and showed the minimum at 50% total reduction. In the case of constant amount rolling, both showed the maximum only at 30% total reduction. Both properties remained almost constant independently of total reduction after the recovery treatment at 100°C for 3h. These behaviors mean that the residual stress induced by rolling is a controlling factor in corrosion. Effects of pass programs, surface contamination and damage were also examined.