Passivation of Al–Cr–Fe and Al–Cu–Fe–Cr complex metallic alloys in 1M H2SO4 and 1M NaOH solutions

The corrosion mechanisms of Al Cr Fe and Al Cu Fe Cr complex metallic alloys have been investigated by potentiodynamic and potentiostatic polarization. Very good passivation of the Al Cr Fe surface is exhibited from 1 M H2SO4 to 1 M NaOH solutions which was confirmed by ICP OES analysis over a period of 273 days. Potentiostatically formed passive films analysed by XPS revealed chromium enrichment in the outermost layer of the aluminium oxy hydroxide film. Although Al Cu Fe Cr showed passivation during potentiodynamic polarization heavy active corrosion at OCP was revealed by ICP OES. For the Al Cu Fe Cr alloy the 10 content of Cr is insufficient to maintain a protective "chemically stable" Cr oxide/hydroxide. (c) 2011 Elsevier Ltd. All rights reserved.