Multifunctional hydrophobic/superhydrophobic protective coatings for magnesium alloys: A review on material design, protection mechanisms, and engineering applications

Magnesium (Mg) alloys have broad application prospects in transportation, biomedical engineering, and marine engineering owing to their low density, high specific strength, and excellent processing properties. However, their inherent susceptibility to corrosion and insufficient service stability urgently necessitate the development of advanced protective coating technologies.

Functional hydrophobic and superhydrophobic coatings are designed by constructing special wetting interfaces that combine micro-/nano-structures with low-surface-energy materials. These coatings not only significantly delay the penetration of corrosive media but also integrate multiple functionalities, such as antibacterial activity, self-healing, anti-icing, antifouling, photocatalysis, and electrical conductivity, thereby realizing a transition from passive isolation to active protection.

This review systematically summarizes the material systems, structural design strategies, protection mechanisms, representative fabrication methods, and recent progress in the application of functional hydrophobic/superhydrophobic coatings for Mg alloys. Particular attention is devoted to the synergistic relationships among surface roughness, porosity, surface energy, and durability, as well as to defect evolution and failure modes under multifield coupled environments.

Addressing current bottlenecks, including the lack of fluorine-free alternatives, insufficient multifunctional integration, complex fabrication processes, and limited long-term service stability, the article highlights future research directions such as green alternative materials, multifunctional modular integration, bioinspired interface reinforcement, and intelligent responsive protection systems.

Collectively, these insights provide theoretical foundations and technical pathways toward achieving long-term, reliable protection and advancing the practical engineering applications of hydrophobic/superhydrophobic coatings on Mg alloys under complex service environments.