Innovative Fabrication Techniques of Superhydrophobic Coatings for Corrosion Protection of Magnesium Alloy (AZ31): A Review

Magnesium alloys, especially AZ31, are widely used as substitutes for plastic, aluminum, and steel due to their low weight and high mechanical performance. These properties make them a key subject of research and a preferred material in many engineering applications, magnesium earning the title of “Green Engineering Material of the 21st Century”. Despite these advantages, their high chemical and electrochemical reactivity cause rapid corrosion when exposed to humid, marine, and chemical environments, leading to structural degradation, increased maintenance costs, and reduced service life in industrial use. To address this limitation, recent research has focused on surface modifications, particularly the development of superhydrophobic (SHP) coatings as a practical, cost-effective solution to enhance corrosion resistance. These coatings reduce contact with corrosive media by combining hierarchical structures with low surface energy materials. This review summarizes the basic principles of wettability and theoretical wetting models, then presents recent advances in SHP coatings for AZ31 alloys. It focuses on standard fabrication methods for developing micro/nano structuring and low surface energy treatments, including hydrothermal synthesis, electrochemical deposition, laser treatment, spraying coating, chemical etching, and micro-arc oxidation. Finally, the paper outlines key challenges and proposes future research directions for improving the corrosion protection of magnesium alloys.