Effect of trace elements on electrochemical properties and corrosion of aluminium alloy AA3102

The purpose of this work is to study the effect of heat treatment and chemical processing on the electrochemical behaviour of aluminium alloy AA3102. Aluminium alloy 3102 was electrochemically activated in chloride solution as a result of heat treatment for periods exceeding 10 min at temperatures higher than 400 degreesC. The electrochemical activation was determined by the presence of deep negative potential transients when exposed to an acidified chloride solution. Furthermore, the anodic current densities became large at a given potential relative to the as-extruded surface as a result of high temperature heat treatment. This activation phenomenon was attributed to enrichment of the surface by lead, which was present in the material as a trace element. Enrichment of lead at the metal-oxide interface was ascertained by GD-OES depth profiling. Chemical and structural changes occurring in the oxide as a result of heat treatment did not have a direct role in the activation process. It was also shown that enrichment of the surface by lead had a sacrificial effect in protecting the surface against pitting corrosion. (C) 2003 Elsevier Ltd. All rights reserved.