Organic-inorganic in-situ hybrid aluminum dihydrogen phosphate binder for enhancing tribocorrosion resistance of ceramic coatings

Abstract

Aluminum dihydrogen phosphate (AP) is modified through organic-inorganic in-situ hybridization and employed as a binder to prepare the chemically bonded phosphate ceramic coatings on AISI 304 L stainless steel. The chemical structure of the hybrid AP binder, mechanical properties and tribocorrosion behavior of the hybrid AP coatings (HAPC) are investigated. The results demonstrate that AP is successfully hybridized with methyltriethoxysilane (MTES) and a chemical structure with P-O-Si as the framework is created. The hybrid AP as a binder improves the hydrophobicity, cohesion and bonding strength of ceramic coatings. In addition, the corrosion current density and total material volume loss of HAPC are lower than those of pure AP coatings, whether under pure corrosion or tribocorrosion. In tribocorrosion experiments, the pure mechanical wear and the wear induced by corrosion dominate the total volume loss of the coating. The filamentous substances generated inside the HAPC enhance the pull-out resistance of the alumina particles and the cohesion of coatings, which can reduce the purely mechanical wear behavior. Besides, the filamentous substances can also fill the holes and cracks inside the coating, extending or blocking the diffusion path of the corrosive medium, which can significantly reduce the friction behavior generated by corrosion induction. Based on these two aspects, the hybrid AP binder effectively enhances the tribocorrosion resistance of ceramic coatings.