The use of coupling agent, 3-aminopropyltiethoxysilane (APTES) in the silanization reaction with metal oxides plays an important role to ensure that additional chemical modification can successfully be achieved. Studies have shown that introducing metal oxides onto graphene oxide sheets can improve the dispersion of sheets in a polymeric matrix, contributing to its excellent anti-corrosion properties. Hence, two methods of APTES attachment has been explored, where the first method utilizes a reflux process to introduce siloxane bonds to the ZnO NP surface; the latter usesuse of ultrasonication to stimulate the functionalization of ZnO NPs. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) were employed to characterize the APTES-Functionalized ZnO and the precipitation on the surface of GO sheets. The effect of GO-ZnO produced by the different types of functionalized ZnO on the corrosion protection and barrier performance of epoxy coating was investigated by electrochemical impedence spectroscopy (EIS). The results revealed that the long duration of reaction time provided by the reflux method managed to increase the number of siloxane bonds on the ZnO surface, allowing more amine groups to be attached onto the GO sheets and thus improve the corrosion resistance of epoxy. © 2018 The Authors, published by EDP Sciences.