Preparation and Anticorrosion Properties of Silane Grafted Nano-silica/Epoxy Composite Coating

2-(3,4-Epoxycyclohexyl) ethyltriethoxysilane (ETEO) was synthesized by a highly effective hydrosilylation reaction using 1,2-epoxy-4-vinylcyclohexane and triethoxysilane as substrates and Karstedt catalyst as the catalyst. Different methods were employed to characterize the coatings. The surface of nano-silica was treated with ETEO in order to obtain a new silane grafted on nano-silica (ETEO-SiO2). The structure of ETEO was characterized by means of H-1 nuclear magnetic resonance spectrometer and Fourier transform infrared spectroscopy. The X-ray photoelectron spectroscopy showed that ETEO was successfully grafted on nano-silica. In addition, the morphology of the coating cross section and dispersion of ETEO-SiO2 were investigated by field emission scanning electron microscopy. The wettability of the coating surface was analyzed by the contact angle measurement. The electrochemical impedance spectroscopy (EIS) and salt spray test of the composite coatings revealed that the corrosion resistance of coatings with ETEO-SiO2 nanoparticles was significantly improved as compared with that of the epoxy (EP) and SiO2/EP coatings. Corrosion resistance achieved the highest value when ETEO-SiO2 content reached 4% (mass fraction). It can be indicated that the SiO2 nano-particles grafted by ETEO enhanced its compatibility effectively in the organic matrix so that ETEO-SiO2 could distribute in the epoxy resin evenly. What's more, the ETEO-SiO2 increased the shielding effect of the coating and filled the coating defects, which can reduce the corrosive diffusion channels and inhibit the progress of the corrosion reaction.