Sequentially bridged biomimetic graphene-based coating via covalent bonding with an effective anti-corrosion/wear protection for Mg alloy

Abstract The industrial applications of Mg and its alloys are restricted by their poor corrosion resistances, owing to the rapid dissolution and hydrogen evolution behaviors. In this study, a sequentially bridged reduced graphene oxide (RGO)/bistriethoxysilylethane (BTSE) coating is successfully grafted on the surface of Mg alloy substrate, to simultaneously inhibit the corrosion and wear behaviors. It exhibits well-aligned biomimetic nacre-like “bricks and mortar” structure connected by covalent bonding networks, consisting of the Si-O-C bonds between the RGO sheets and the Si-O-Si bonds derived from BTSE self-crosslinking reactions. The reduced porosity and defects lead to a high continuity and integrity of the RGO/BTSE coating, which decreases the corrosion rate by an order of magnitude compared with bare Mg substrate and RGO coated sample, owing to the enhanced barrier effect and weakened galvanic corrosion. In addition, the hybrid coating also performs well anti-wear property due to the intrinsic lubrication of RGO sheets, which can protect the substrate from friction and wear. The wear rate decreases from 3.5 × 10−3 mm3N-1 m-1 of bare Mg alloy to 5.13 × 10-5 mm3N-1 m-1 of RGO/BTSE coated sample. The interlayer slipping between the RGO sheets effectively decreases friction resistance, although the incorporation of BTSE slightly increases their shear resistance.