Enhancing the barrier effect of sol-gel derived inorganic coating by doping h-BN nanosheet

Abstract Nanocomposites filled with impermeable two-dimensional materials are of specific interest for protecting metal from corrosion. The addition of hexagonal boron nitride nanosheet (BNNS) into a coating matrix can improve the barrier effect virtually due to its high chemical and thermal stability and dielectric property. This atom-level thick filler involves a «tortured pathway» that prolongs the penetration distance to the substrate. In this study, BNNS was added into a zirconium coating prepared via sol-gel way. In order to understand the influence of nanosheets size on the barrier performance, three h-BN grades were used. It was intended to keep all the other elaboration parameters constant so that the electrochemical behavior variation is mainly attributed to the nanosheet size. The morphology and microstructure of hexagonal boron nitride flakes in different exfoliation level and the nanocomposite coating were studied by SEM, HRTEM, SAED, FTIR cartography, Raman spectroscopy. Meanwhile, the corrosion resistance of composite coatings was characterized by polarization test and long-term electrochemical impedance spectroscopy in a 3.5 wt% NaCl solution.