Effect of heat treatment on electrochemical behaviour of aluminium alloy AA3005

The effect of heat treatment on the electrochemical properties of bare meta l samples of aluminium alloy 3005 in an acidified sodium chloride solution was investigated. Annealing at increasing temperatures in the range 150-500 degreesC causes negative potential transients of increasing magnitude and longevity for samples exposed at open circuit. Electrochemical characterisa tion shows the potential transients to be caused by an increased anodic rea ction rate of the annealed material surfaces as compared to the cold rolled , hard temper substrate. It is suggested that this increased anodic activit y 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 t he high temperature heat treatment. The mechanisms controlling short term e lectrochemical properties of bare metal samples may not be identical to tho se controlling the filiform corrosion susceptibility of coated products and a cautious approach is recommended when using electrochemical techniques f or predicting corrosion properties. (C) 2001 Elsevier Science Ltd. All righ ts reserved.