Alkaline-based surface modification prior to ceramic-based cerate conversion coatings for magnesium AZ91D

Abstract

The effect of surface modification prior to cerate coatings on the corrosion behavior of magnesium was investigated. A series of samples were modified under different conditions before ceria treatment. Electrochemical impedance spectroscopy and polarization measurements were used to determine the optimum conditions for corrosion protection. Generally, cerate can be used as a localized corrosion inhibitor. The level of inhibition strongly depends on the ceria concentration. Alkaline etching is more effective in reducing the pitting corrosion than acidic etching. Alkaline etching plays an important role in inhibiting the active surface sites, rejecting the chloride ions from the surface, and forming uniformly distributed oxide film. © 2007 The Electrochemical Society.