Graphene oxide encapsulated by mesoporous silica for intelligent anticorrosive coating: studies on release models and self-healing ability

Abstract

Conductive graphene accelerates localized corrosion at exposed coating-metal interfaces as a cathode, which impedes its applications in metal protection. Nevertheless, graphene-polymer coatings are still the best option due to the original impermeability and chemical stability once the galvanic coupling is cut. However, it is difficult to guarantee the miscibility when graphene is employed as the nanofiller. Herein, a bi-layered nanocomposite coating with self-healing capability at the functional level that ensures strong interfacial interaction is reported in this work. Unlike previous nanofiller coatings, the coating with the benzotriazole-loaded nanoreservoir intermediate layer structure and poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) topcoat was fabricated via the dip-coating and spin-coating technique, respectively. An efficient nanoreservoir with a thickness of 35 nm for corrosion inhibitor delivery was synthesized by a combination of the oil–water stratification method and vacuum loading. Semiempirical models, which have scarcely been reported on corrosion inhibitor release, were blazed to predict the diffusion mechanism. The corrosion resistance was evaluated by electrochemical characterization. With a nanoreservoir loading of 0.25 g/(20 mL ethanol), the bilayer nanocomposite coating not only improved the barrier properties, but also showed self-healing ability for long-term protection. This strategy provides a candidate for the development of graphene-based anticorrosion coatings.