Simultaneously improved corrosion/wear resistances of epoxy coating on Mg alloy via the coupled hybridization of GO and nano-SiO2

The extensive application of Mg alloys is restricted by their poor corrosion, wear resistances and long-term service performance. Although the low-cost epoxy (EP) coating has excellent corrosion resistance, many pores and cracks are easily formed during the curing process, leading to the deterioration of barrier capacity. This study reports an epoxy-based nanocomposite coating, fabricated through the hybridization of γ-(2, 3-epoxypropoxy) propytrimethoxy silane modified silica nanoparticles and graphene oxide (mSiO2/GO). The insulating SiO2 particles can isolate the direct contact between Mg alloy substrate and GO sheets, avoiding the formation of micro-cells and preventing the galvanic corrosion. The SiO2/GO in EP coating with “crack pinning and bridge” structure has reduced porosity and enhanced consistency, which effectively prevents crack propagation and electrolyte penetration. The corrosion rate of SiO2/GO/EP coating is 374 and 10 times lower than that of pure EP coating and individual GO/EP coating, respectively. The wear rate of GO/EP and SiO2/GO/EP coating specimens is 81.2 % and 70.4 % less than that of the pure EP coating, which is related to the favorable lubricating performance and high hardness of GO nanosheets. The results show that the embedding of well-distributed mSiO2-GO hybrids can remarkably improve the barrier effect and anti-corrosion of EP coating.