Effects of graphene on the corrosion evolution of zinc particles in waterborne epoxy zinc-containing coatings

In this paper, graphene/ waterborne epoxy zinc-containing coatings with different graphene contents were prepared. The corrosion resistance properties of the graphene/ waterborne epoxy zinc-containing coatings were investigated by electrochemical impedance spectroscopy (EIS), immersion test and neutral salt spray test. The results showed that addition of 0.6 wt% graphene into the coating could remarkably improve its cathodic protection performance and barrier performance comparing with the coating without graphene. In addition, the effects of graphene on the corrosion evolution of zinc particles in the coating were observed by the field-emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS). The results showed that the zinc particles near the interface between steel substrate and the coating corroded firstly after the corrosive media diffused in the coating and reached the interface due to the cathodic protection to the steel, and then zinc particles continued to be corroded from the interface to upper part of the coating since they could provide the cathodic protection to the substrate thanks to the electrical connection of graphene. Meanwhile, X-ray diffraction (XRD) patterns confirmed the corrosion products of the zinc particles were mainly consisted of Zn5(OH)8Cl2·H2O.