Superior corrosion resistance and thermal/electro properties of graphene−epoxy composite coating on Mg alloy with biomimetic interface and orientation

Biomimetic graphene−epoxy composite coating was fabricated with a “brick and mud” structure via a spin-coating strategy. Imidazolium-based ionic liquids modified graphene (GI) was synthesized to improve the interfacial compatibility between the graphene (G) layers and epoxy resin. The surface morphology and chemical structures were observed and analyzed through scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) as well as Fourier transform infrared spectroscopy (FTIR). The thermal imager was used to record the temperature change on the surface. The surface resistivity and thermal conductivity of the coating were determined via volumetric surface area resistivity tester and laser flash method, respectively. The corrosion resistance was investigated through electrochemical impedance spectroscopy (EIS) and salt spray testing. The GI layers in the composite coating exhibited a near-parallel orientation, which led to improved heat transfer and electrostatic dissipative efficiency. The through-plane thermal conductivity and surface resistivity were 0.77 W·m −1 ·K −1 and 1.6×10 6 Ω·cm, respectively. Electrochemical impedance spectroscopy tests revealed that the low-frequency modulus of the coating reached 6.76×10 10 Ω·cm 2 after 40 d of immersion, which was about two orders of the magnitude higher than that of the pure epoxy coating, showing a superior corrosion resistance.