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Published online by Cambridge University Press: 01 February 2011
Commercial alloy AA8006 (nominal composition in wt%1.5Fe, 0.4Mn, 0.2Si) exhibits electrochemical activation in chloride media as a result of annealing at temperatures above 350°C. Activation is manifested by a significant negative shift in the corrosion potential and a significant increase in the anodic current when polarized above the corrosion potential in aqueous chloride solution. This phenomenon was correlated with the enrichment of trace element Pb at the oxide-metal interface. For fixed annealing time, maximum activation and Pb-enrichment are obtained at an annealing temperature of 450 °C independent of the original surface condition. Reduced activation with increasing temperature is attributed to increasing density of the spinel crystalline phase to cause the passivity of the surface.