Evaluation of the micro-arc oxidation treatment effect on the protective performance of a Mg-rich epoxy coating on AZ91D magnesium alloy

A micro-arc oxidation (MAO) film is prepared on AZ91D magnesium alloy, and the effects of the MAO treatment on the performance of a Mg-rich primer on AZ91D alloy are studied. After MAO treatment, an oxidized film with high porosity forms on the magnesium substrate. As a result, the adhesion of a Mg-rich primer to the AZ91D substrate increases. The MAO treatment significantly improves the performance of a Mg-rich primer on the AZ91D alloy, owing to the corrosion resistance of the MAO film. The coating system with MAO pre-treatment shows good barrier effects after 2400 h of salt spray testing and could serve to protect the AZ91D alloy below.