A brief review on Zn-Mg-Al (ZMA) coated steels: Linking microstructure to corrosion performance

Hot-dip metallic sacrificial coatings is one of the most preferred solutions to enhance the corrosion performance of steels. The application of hot-dip Zn-Mg-Al (ZMA) coating for protecting steel structures from corrosion has gained significant attention in recent times owing to their superior corrosion resistance and mechanical properties compared to conventional zinc based hot-dip coatings. This succinct review examines the corrosion protection mechanisms of hot-dip ZMA coatings on steel substrates. The primary objective of the study is to comprehend the individual and synergistic effects of Zn, Mg, and Al on the microstructural evolution and corrosion behavior of the ZMA coatings. Further, the corrosion mechanisms of ZMA coated steel in chloride-rich aqueous environments are reviewed, in conjunction with the mechanism of black rust formation. Furthermore, this review examines key factors governing the long-term corrosion performance of the ZMA coatings and outlines emerging research directions to enhance their durability and environmental sustainability.