Abstract
Increased recycling of aluminum alloys is a necessity inview of increasing demand for the material andenvironmental concerns related to primary production. Aconsequence of recycling is an appreciable increase in thetype and amount of impurity and trace elements that cansignificantly affect the properties. Low melting pointmetals of Group IIIA-VA are known to activatealuminum, as characterized by pitting potential depressionand high anodic currents produced in the potential regionexpected normally to be passive. Activation can bringabout galvanic corrosion and filiform corrosion. It istherefore important to understand the mechanisms bywhich these elements cause electrochemical activation.Among these, Pb, which is present in almost all aluminumalloys at the ppm level, has received significantattention. Activation is attributed to Pb segregating inthe form of nanosize metallic film and particles at theoxide-metal interface as a result of annealing at 600C,and thereby destabilizing the oxide in chloride solution.The active surface is further characterized by the presenceof at least two oxidation peaks in the potentiodynamicpolarization curve, the nature of which is not yetunderstood. The purpose of this work is to provideadditional information about the cause of such phenomenaby simultaneous observation of the corroding surfaceduring potentiodynamic polarization.