The waterborne epoxy composite coatings with modified graphene oxide nanosheet supported zinc ion and its self-healing anticorrosion properties

In this study, a waterborne epoxy coating with the dual functions of self-healing and anti-corrosion was obtained through nanocomposites of (GO@(PDA + KH-550)-Zn). GO@(PDA + KH-550-Zn) was prepared by grafting dopamine (DA) with a silane coupling agent (KH-550) onto a graphene oxide (GO) backbone, and by then loading zinc ions to obtain modified GO nanocomposites. The GO modified through the formation of GO@(PDA + KH-550)-Zn was uniformly dispersed in the water-based epoxy coating. The results of anti-corrosion tests showed that the GO@(PDA + KH-550)-Zn/WEP composite coating recorded its highest impedance value of 2.14 × 109 Ω·cm2 after 26 days, where this was three orders of magnitude higher than that of a blank water-based epoxy coating (WEP). It still had a high impedance value of 8.71 × 108 Ω·cm2 after 32 days, with a rate of corrosion of 0.007 mm/year. The self-healing performance of the GO@(PDA + KH-550)-Zn/WEP composite coating containing scratches was verified by electrochemical impedance spectroscopy (EIS) tests. Scanning electron microscope (SEM) images showed that intermediate scratches on the GO@(PDA + KH-550)-Zn composite coating had been repaired, probably due to the release of a corrosion inhibitor (Zn) due to the peeling of the PDA from the surface of the GO. When the electrolyte penetrated into the coating, the release of zinc ions led to the formation of oxide films on the cracks, and the PDA was able to anchor ferrous or trivalent iron cations (Fe2+/Fe3+) to promote the adhesion and bonding of the composite coating by exerting a unique self-healing function.