Superhydrophobic coatings on concrete and steel: mechanisms, preparation methods, applications, and future...

Concrete and steel are indispensable to modern infrastructure, but their long-term service is severely limited by corrosion, water ingress and environmental degradation. Superhydrophobic coatings have therefore emerged as an attractive protection strategy because their hierarchical micro/nanostructures, combined with low-surface-energy chemistry, can reduce liquid adhesion, hinder the penetration of water and corrosive species, and retard interfacial deterioration. This review summarizes recent advances in superhydrophobic coatings for concrete and steel, with emphasis on the distinct substrate-dependent requirements associated with porous cementitious matrices and dense metallic surfaces. After briefly outlining the wetting basis, representative fabrication routes are discussed, including sol-gel-assisted methods, spraying, brushing, dip coating, templating, in situ biomineralization, electrochemical deposition, layer-by-layer assembly, solvent-free fabrication, laser texturing and spin coating. Their practical roles in corrosion protection, barrier enhancement, anti-icing, self-cleaning and environmental resistance are then examined in relation to realistic service conditions. Particular attention is given to the interplay of hierarchical roughness, surface chemistry and coating-substrate interfacial anchoring, which jointly governs durability and functional stability. Current limitations, especially in mechanical robustness, long-term immersion stability, environmental adaptability and scalable application, are also highlighted, together with emerging opportunities such as waste-derived systems, antibacterial surfaces and self-healing coatings.