Synergistic Anticorrosion Mechanism of KH560-Modified TiO2/ECTFE Coatings via Photogenerated Cathodic Protection and Barrier Effects

In this study, a surface grafting modification strategy for TiO2 using the silane coupling agent γ-glycidoxypropyltrimethoxysilane (KH560) was employed, and a fluororesin-based anticorrosion coating with synergistic photogenerated cathodic protection and physical barrier effects was prepared by electrostatic spraying followed by thermal treatment. By combining microstructural characterization, photoelectrochemical performance analysis, and molecular dynamics simulations, the mechanisms by which photoresponsive behavior enhances corrosion protection performance were systematically investigated. The results indicate that KH560 can condense with surface hydroxyl groups on TiO2 to form Ti–O–Si covalent bonds, effectively suppress TiO2 agglomeration, and improve TiO2 dispersion and interfacial compatibility within the ethylene-chlorotrifluoroethylene (ECTFE) matrix, thereby producing a denser physical barrier. The long alkyl chains of KH560 further enhance the coating’s hydrophobicity (water contact angle = 96.8°). After modification, the coating showed a marked increase in photocurrent density, which is attributed to an enlarged photoresponsive area and improved charge-carrier separation efficiency resulting from better dispersion. This promotes migration of photogenerated electrons to the metallic substrate and enables sustained photogenerated cathodic protection. Consequently, in 3.5 wt % NaCl solution, KH560-TiO2/ECTFE exhibited optimal long-term protective performance under both lighting and dark conditions, and an appropriate TiO2 loading combined with surface modification did not readily induce oxidative degradation of the coating matrix. Molecular dynamics simulations revealed that KH560 modification reduces the system’s free-volume fraction and strengthens interfacial interactions between TiO2 and ECTFE, thereby effectively suppressing the diffusion of water molecules and chloride ions (with diffusion coefficients as low as 0.896 × 10–9 m2/s and 1.928 × 10–10 m2/s, respectively).