Effect of heat treatment on electrochemical behaviour of aluminium alloy AA3005

Abstract The effect of heat treatment on the electrochemical properties of bare metal samples of aluminium alloy 3005 in an acidified sodium chloride solution was investigated. Annealing at increasing temperatures in the range 150–500°C causes negative potential transients of increasing magnitude and longevity for samples exposed at open circuit. Electrochemical characterisation shows the potential transients to be caused by an increased anodic reaction rate of the annealed material surfaces as compared to the cold rolled, hard temper substrate. It is suggested that this increased anodic activity during short time exposure of the bare metal samples may be attributed to changes in the protective properties of the surface oxide as a result of the high temperature heat treatment. The mechanisms controlling short term electrochemical properties of bare metal samples may not be identical to those controlling the filiform corrosion susceptibility of coated products and a cautious approach is recommended when using electrochemical techniques for predicting corrosion properties.