Electrochemical behavior of a chromated 55mass%Al-Zn coated steel sheet before and after a heat treatment

Abstract

The electrochemical behavior of hot-dip 55% Al-Zn coated steel sheets with and without the chromating treatment before and after annealing by means of DC anodic voltammetric technique is studied. Even after the heat treatment the chromating affects the voltammograms. The current densities in the voltammograms of the chromated samples are smaller than those of chromated samples even after heat treatment. The residual passivation decreases as the heat treating temperature increases. Dissolution proceeds slowly stating from the top surface on the few spots of interdendritic zinc. After heat treatment some of the chromate layer is lost and more interdendritic zinc areas can be dissolved.