Among the corrosion prevention methods of magnesium alloys, organic protective coating is widely used for its simple construction, economical application, free from the constraints of equipment shape and certain decorative effect. Therefore, developing suitable coating system for magnesium alloy is an economical and effective way to improve its anti-corrosion properties. In the protection system of magnesium alloy, it is very necessary to select the multilayer composite coating system correctly.

Magnesium alloy has strong electrochemical activity, with a standard electrode potential of -2.37V. It is easy to corrode and passivate in humid, CO2 and CL environment, and can naturally form basic carbonate in the air. Therefore, the protection of the film is poor. At the same time, impurities and alloying elements in magnesium alloy are easy to cause galvanic corrosion, stress corrosion and fatigue corrosion in the process of use, which greatly limits the extensive application of magnesium alloy materials.

In order to improve the corrosion resistance of magnesium metal, from the point of view of alloy design and improving casting conditions, the impurity content should be reduced, alloying elements should be added, and the surface of high pure gold should be generated with protective film or coating, to improve and improve the corrosion resistance. Reducing the content of impurities by metallurgy, or adding other alloying elements to limit the presence of impurities and improve the corrosion resistance of magnesium alloys will further expand the application range of magnesium alloys. However, this method is limited to adding rare earth elements and other elements, which has not been widely used and cannot meet the industrial requirements. Then some new surface treatment methods such as tin conversion film, laser surface treatment, PVD(physical gas phase precipitation), chromium nitride coating, magnesium alloy surface deposition of aluminum and other methods also emerged. Surface modification is mainly divided into electrochemical method, chemical method, hot working method, high vacuum method and other physical methods.