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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. Image 1 [ABSTRACT FROM AUTHOR]

Poor corrosion and wear resistances of Mg alloys have severely restricted their extensive applications. Here we report a comparative study of bioinspired graphene oxide(GO)/reduced graphene oxide (rGO)-polyvinyl alcohol (PVA) composite films with nacre-like architectures on Mg alloys, via a facile reduction process. GO-PVA film remarkably deteriorates the corrosion resistance of Mg alloy, with an increased corrosion rate of 3.657 × 10−5 from 2.038 × 10−5 A/cm2, due to its loose microstructure and typical cathodic reaction. In contrast, the removal of oxygen-containing groups by chemical reduction leads to a recovery of conjugated structure and reduces the intrinsic capillaries, and the corrosion rate of rGO-PVA film is 18 times lower than that of GO-PVA film, through hindering the galvanic corrosion and weakening the cathodic reaction. Additionally, the wear rate of Mg alloys protected by GO/rGO-PVA films remarkably decreases by 98.6% and 98.2%, respectively. The chemical reduction effectively decreases the cluster-stacked structure on the surface of the GO-PVA film and restricts its exfoliation behavior, which promotes the puckering effect and results in a slightly enhanced wear behavior of the rGO-PVA film. The current study demonstrates a potential prospect of the bioinspired graphene-based film, which is beneficial to achieving the integrated anti-corrosive/wearable performances of metallic materials. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Mg and its alloys generally exhibit the poor corrosion and wear resistances, which greatly limits their industrial applications. Inspired from an ordered layered structure within natural nacre, the homogeneous reduced graphene oxide/poly (vinyl alcohol) (RGO/PVA) coating is successfully fabricated on Mg alloy surface in the current study, through a facile spin-assisted layer-by-layer assembly (SA-LBL) technology. The hybrid hydrogen/covalent bond networks form between PVA chains and RGO sheets, resulting in a compact lamellar "bricks-and-mortar" structure. The microstructure of hybrid coating is strongly influenced by the cross-linking effect of PVA molecule, whose suitable content is beneficial to generating the densely stacked lamellar coating with excellent binding strength and reduced intrinsic defects, which can significantly improve its corrosion resistance. And the water molecules can hardly diffuse into the hybrid coating, leading to a long-term stability of samples in aqueous solution, ethanol and N, N-dimethylformamide. Besides, the high hardness and good lubricant effect of RGO sheets confer the hybrid coatings outstanding wear-resistant properties. Therefore, the bio-inspired RGO coating with a certain amount of PVA allows it to have a superior barrier effect and maintain the lubrication, which can provide an integrated protection for the corrosion and wear behaviors of Mg alloy. Graphical abstract Image [ABSTRACT FROM AUTHOR]

The poor corrosion and wear resistances hinder the industrial applications of magnesium and its alloys. In this paper, a new graphene oxide (GO) coating is fabricated on the surface of extruded Mg-Zn-Ca alloy, via the silane coupling agent. The GO coating has fully covered the Mg substrate through the chemical reactions, and formed an overlapped multilayer structure by interlocked effects. Electrochemical measurements indicate that the anti-corrosion performance can be remarkably improved by silane/GO coating, because the stable covalent bonds within the coating effectively restrict the penetration of electrolyte into the Mg surface, representing an excellent corrosion barrier effect. The GO coating drastically promotes the wear resistance, due to the superior bonding between the Mg substrate and GO sheets with high hardness and good lubricant effect. [ABSTRACT FROM AUTHOR]