Corrosion Protection of Graphene-Modified Zinc-Rich Epoxy Coatings in Dilute NaCl Solution

In order to hold the excellent corrosion resistance of zinc-rich epoxy coatings with reduced zinc content, five types of graphene modified zinc-rich epoxy coatings (G-ZRCs) were prepared. The effect of zinc content on the corrosion protection behaviors of G-ZRCs was investigated using electrochemical impedance spectroscopy (EIS). Open circuit potential (OCP) was also utilized to deepen the understanding of the anticorrosion mechanism of the as-prepared composite coatings. The results confirmed that addition of 0.3 wt % graphene could make the coating with 40 wt % (G-40ZRC) and 55 wt % zinc (G-55ZRC) provide cathodic protection for a short period of time. The EIS and OCP results showed a dominant physical barrier protection mechanism for the coatings without zinc (G-ZRC), while there was a mixed mechanism for G-40ZRC and G-55ZRC and a dominant cathodic protection mechanism for the coatings with 70 and 85 wt % zinc (G-70ZRC and G-85ZRC). Furthermore, the graphene modified zinc-rich coatings and corresponding corrosion products immersed in a 3.5% NaCl solution for 100 days were also characterized, which could further reveal anticorrosion mechanisms of the graphene modified zinc-rich coatings and the passivation effect of polyaniline (PANI).