Passivation and potential fluctuation of Mg alloy \AZ31B\ in alkaline environments
By Shengxi Li and Ana C. Bacco and Nick Birbilis and Hongbo Cong
Published in Corrosion Science
2016
Abstract
The passivation and corrosion behaviors of Mg alloy \AZ31B\ were investigated in chloride-free NaOH solutions with pH range from 10 to 14. The results indicate that various phases behave differently at different pH levels. Al-Mn intermetallics serve as strong cathode at pH ? 11, but dissolve at pH ? 13. Ambient oxygen is responsible for the potential rise at pH ? 13 and subsequent significant potential oscillation (>1 V) is attributed to the passive film breakdown at the intergranular boundaries in the oxide film. Optimal passivation is achieved at pH 12 with thin uniform passive film formed across the surface.