Micro-Arc Oxidation of Magnesium Alloys：Lightweight Materials Review

Magnesium alloys are the most potential lightweight high-strength structural materials, which can significantly reduce the curb weight of electric vehicles, extend the driving range and reduce carbon emissions. However, magnesium alloys have high chemical activity and are easy to be corroded. Micro-arc oxidation is a wet surface treatment process controlled by multi parameters. By this way, a dense ceramic protective film can home-position grow up on the surface of magnesium alloys, which improves the corrosion resistance. Voltage pulse mode, current density, frequency and duty ratio and electrolyte characteristics can significantly affect the structure of ceramic coating on the surface of magnesium alloys. Micro-arc oxidation process has several advantages, such as simple cleaning and pretreatment, insensitivity to electrolyte composition and ambient temperature, and dividable implementation. The main challenges are that the supporting equipment need to be further improved, the oxidation voltage and system energy consumption are high, and the electrolyte temperature rises too fast so that it requires a large volume of cooling and heat exchange equipment. Furthermore, the growing mechanism of ceramic film should be clarified.