Review of Oxide Coatings Containing ZrO2 on Magnesium Alloys by Microarc Oxidation

Microarc Oxidation (MAO) technology can prepare a ceramic-like oxide coating. It is an effective technique to increase the wear and corrosion resistance of magnesium alloys. The MAO coating has many defects such as holes and cracks. As well, the coating on magnesium alloys typically consists mainly of MgO, which absorbs water or dissolves in a humid or acidic environment. Therefore, the MAO coatings are not adequate for the long-term protection of magnesium alloys. MAO coatings that are composed of ZrO2, or which have ZrO2 with a compact microstructure, can improve the protection of magnesium alloys. This paper critically summarizes the progress of MAO coatings containing ZrO2 on magnesium alloys from four aspects: electrolyte compositions, electrical parameters, the two-step MAO process, and post-treatment of MAO coating. The future research directions for MAO coatings containing ZrO2 on magnesium alloys are discussed.