Emerging progress of chemical-based coating for the corrosion protection of magnesium alloys: a review

Magnesium (Mg) and its alloys are preferred materials for lightweighting, particularly for automotive and biomedical applications due to their outstanding biocompatibility and osseointegration properties. However, the use of Mg in many applications is constrained by its poor corrosion resistance; hence, intensive investigations are needed to improve its anti-corrosion stability. Among the methods for increasing anti-corrosion stability, a protective layer coating on Mg has been demonstrated to be very efficient. Herein, we provide an overview of the current state and development of chemical-based coatings applied to Mg alloys, including anodizing, plasma electrolytic oxidation, electrodeposition, electroless plating, chemical conversion coating, sol-gel coating, layered double hydroxide, and layer-by-layer assembly. The emerging progress in coating fabrication and corrosion performance breakthroughs are disclosed, and coating mechanisms and functional perspectives are explored. Because of significant progress in developing corrosion protection approaches for Mg alloys, there is a vast possibility of chemical-based coatings waiting to be explored. Despite significant advancements in the technology and development of future functional and smart coatings for Mg alloys, a traditional or conventional chemical-based coating retains comparative functional qualities, hence, necessitates a deeper understanding of several important aspects, including coating ease of fabrication, coating strength, and actual anti-corrosion performance.