Multilayer structural epoxy composite coating towards long-term corrosion/wear protection

The corrosion-promotion effect caused by the high conductivity of graphene (G) cannot meet the requirement of long-term protection of G-containing coating under the increasingly complex working condition. Herein, a multifunctional epoxy (MF) composite coating with multilayer structure is constructed containing bottom nano-Al2O3/epoxy layer, intermediate G/epoxy layer, and top nano-SiO2/epoxy layer via a layer-by-layer (LBL) assembly method to improve the corrosion resistance, UV resistance, and tribological properties. MF composite coating exhibits an improved impedance value increased by 10 times and the excellent long-term chlorine resistance, mainly depending on the formation of tortuous diffusion path and avoiding the galvanic corrosion between G and metal substrate. Its wear rate (1.59 × 10−7 mm3/N·mm) is decreased by 73.54% compared with pure epoxy coating due to the lubrication effect of nanofillers and the increase of coating crosslinking density. Moreover, the improved UV aging resistance is reflected in the unchanged chemical structure after 30 days of exposure in UV irradiation, which is attributed to the absorption and reflection of UV light by the nanofillers. Therefore, the as-prepared multifunctional coating has great application prospects in materials protection.