An Impact of the Recent Developments in Coating Materials and Techniques on the Corrosion Response of AZ91D Alloy: A Review

AZ91D, a die‐casted alloy, offers several benefits (better saltwater corrosion resistance, suitable castability, and good atmospheric stability) over other grades of magnesium alloy. However, it cannot overcome the challenging requirements of advanced applications in its current form. Extensive research in coating technologies is crucial in enhancing the performance of AZ91D alloy in highly corrosive environments (coastal and marine, industrial, farm, etc.). The high corrosion resistance of AZ91D for various applications is achievable through the deposition of different materials. Developments in coating materials and techniques, with their influence on the corrosion protection behavior of AZ91D alloy, over the last decade (2012–2022), are focused on in this study. It is observed that composite, biodegradable, and self‐healing coatings are gaining popularity. The transition in the coating technology, from conventional to self‐healing coating materials and from conventional to environment‐friendly coating techniques, is a vital part of this discussion. This review further explores how different additives, pre‐treatments, post‐treatments, and corrosion inhibitors affect the corrosion performance of coatings. This study helps select the optimum coating material for AZ91D magnesium alloy to fulfil a specific application requirement and guides toward technological developments in this segment.