Fabrication of hydrophobic and enhanced anticorrosion performance of epoxy coating through the synergy of functionalized graphene oxide and nano-silica binary fillers

Two-dimensional graphene oxide (GO) nanosheets have emerged as ideal nano-fillers in anticorrosive epoxy coatings, but their poor dispersion because of pi-pi interaction, high hydrophilicity, and low compatibility with epoxy resin limit their application. In this work, to conquer these obstacles, the hydrophobic and anticorrosive GO based epoxy composite coating was developed via the synergistic enhancement effect of binary nano-fillers. To achieve this goal, the graphene oxide and nano-silica (SiO2) were hydrophobically functionalized by the 1H,1H,2H,2H-perfluoro-decyl triethioxy silane (PFDS) via a simple grafting method (SiO2-P: mSiO(2): mPFDS=1:1), GO-P-3: mGO:mPFDS=1:3), which were applied as binary fillers to reinforce the epoxy coating with enhanced dispersion and compatibility with matrix. Benefiting from the hierarchical micro-/nano- structure, regulated surface energy, good dispersion, and synergy of SiO2-P and GO-P3 binary fillers, the epoxy composite coating showed greatly enhanced hydrophobicity (The water contact angle increased from 70.45 degrees to 126.84 degrees) and anti-corrosion performance. With the synergetic enforcement of 1.5 wt % SiO2-P and 0.5 wt % GO-P-3, the prepared epoxy composite coating exhibited the best anticorrosive performance with impedance of 2.74 x 10(9) Omega center dot cm(2) (0.01 Hz) after immersion in 3.5 % NaCl medium for 30 days, which was confirmed by the salt spray test results. Meanwhile, the anti-corrosion mechanism including hydrophobicity and prolonged diffusion path of water-soluble corrosive medium was tentatively discussed.