Interfacial Regulation of Hard-Anodized Aluminum Alloy for Fabrication of a Wear-Resistant Superhydrophobic F-SiO2@PU Composite Coating with Enhanced Long-Term Corrosion Protection

Conventional superhydrophobic coatings on aluminum alloys are frequently limited by inadequate coating–substrate adhesion, poor mechanical robustness, and the vulnerability of their surface micro/nanostructures to mechanical damage. To address these challenges, a hydroxyl-rich anodic oxide interlayer was formed via hard anodization followed by a hydroxylation treatment, thereby enhancing interfacial bonding and providing abundant active anchoring sites for coating deposition. Using this interface-engineering strategy, a mechanically durable superhydrophobic F-SiO2@polyurethane (PU) composite coating with hierarchical micro/nanostructures was successfully fabricated on aluminum alloy substrates through a facile spray-coating process. The anodized substrate provides abundant hydroxyl groups and interfacial anchoring sites, while the PU matrix enhances structural integrity and facilitates particle fixation. Incorporating fluorinated SiO2 nanoparticles produced a hierarchical micro/nanostructure with low surface energy. After 10,000 cm of abrasion and 200 tape-peeling cycles, the coating maintained contact angles above 150°. The coating maintained superior corrosion resistance during prolonged immersion in acidic, alkaline, and saline environments. The improved durability and corrosion resistance originate from the synergistic effects of strong interfacial bonding, polymer barrier protection, and the fluorinated hierarchical structure. This study offers a promising strategy for developing durable superhydrophobic coatings for long-term protection of aluminum alloys.