Inhibited corrosion activity of biomimetic graphene-based coating on Mg alloy through a cerium intermediate layer

The poor corrosion/wear resistance of Mg alloy seriously limits its industrial application. Graphene-based anti-corrosion coatings show the excellent imperviousness, but they can provide the additional cathodic sites for Mg alloys, which accelerates the galvanic corrosion behaviors near the interfaces. A novel design of cerium-based intermediate layer (Ce(IV)) is reported in this study, which exhibits a synergistic effect of hydrogen/ionic bond on the graphene oxide (GO)/polyvinyl alcohol (PVA) biomimetic coating. It overcomes the problems of galvanic corrosion and low interfacial adhesion between Mg substrate and hybrid coating through a prominent barrier effect. Furthermore, the GO/PVA coating with bricks and mortar structure effectively blocks the permeation of electrolyte due to the reduced porosity and enhanced densification. The corrosion rate of Ce(IV)/GO/PVA coating is 11 and 19 times lower than bare Mg alloy and single GO/PVA film, respectively. The wear rate of GO/PVA and Ce(IV)/GO/PVA samples is decreased by 98.8% and 97.6%, which is ascribed to the high hardness and lubrication of GO sheets. Moreover, the relatively interlayer slipping between GO sheets can lubricate the sliding process. Compared with GO/PVA, the slightly decreased wear resistance of Ce(IV)/GO/PVA coating is resulted from the enhanced shear force. (C) 2020 Elsevier Ltd. All rights reserved.