Investigation of the anticorrosion properties of graphene oxide-modified waterborne epoxy coatings for AA6061

Abstract

In this study, the two-dimensional material graphene oxide (GO) was modified by a quaternary ammonium salt (Dimethyloctadecyl[3-(trimethoxysilyl) propyl] ammonium chloride (TPOAC)) and then introduced into the waterborne epoxy (WEP) coatings to improve the corrosion resistance of the WEP coatings on the aluminum alloy substrate. TPOAC as a modifier not only improves the compatibility of GO with the polymer coatings, but also greatly reduces the internal defects of the WEP coatings. Scanning electronic microscopy (SEM) images show that the composite WEP coatings are denser and internal defects are greatly reduced. Electrochemical test (electrochemical impedance spectroscopy (EIS)) was used to evaluate the corrosion resistance of the WEP coatings. Consequently, after being immersed in 3.5 wt% NaCl solution for 30 days, modulus at lowest frequency (2.7 × 107 Ω cm2) of the composite WEP coating reveals two orders of magnitude higher than that of blank WEP coating (5.6 × 105 Ω cm2). The results show that the modified GO enhances the penetration resistance of WEP coatings to corrosive media and improves the long-term anticorrosion protection performance of WEP coatings on aluminum alloy substrate.