Preparation of corrosion resistant film on magnesium alloys with different aluminum contents by steam coating

Magnesium alloys are highly desirable in the fields of electronic and transport industry. However,they have a significant disadvantage in corrosion resistance. Thus, the preparation of protective film on the Mg and its alloys is required to improve the corrosion resistance. Unfortunately, typical surface treatment on Mg Alloys such as chromate treatment are highly toxic.We proposed a novel and environmentally friendly coating method for Mg alloys, that is, steam coating. Steam coating is a chemical free method and only pure water is used as a steam source. In this study, we aimed to fabricate corrosion resistant films on Mg alloys with different aluminum contents (AZ31, AZ61, AZ91D) by steam coating. XRD patterns of all films demostrated that all films were composed of Mg(OH)2, AlOOH, and Mg-Al layered double hydroxide (LDH). SEM observation revealed that all substrates were completely covered with the film. Potentiodynamic polarization curve measurements showed that the corrosion resistance of the film coated Mg alloys was considerably improved compared to untreated Mg alloy despite types of Mg alloys.