Nafion-Endowed Graphene Super-Anticorrosion Performance

Application of graphene (Gr)-reinforced green waterborne epoxy (WEP) coatings faces two major challenges: one is the usage of hydrophilic dispersants that can weaken the interactions between emulsifiers/WEP, resulting in demulsification of the WEP matrix, and the other is the "corrosion promotion activity (CPA)" originated from the high electric conductivity of Gr itself, which restricts the long-term anticorrosion capability. Herein, effective electrostatic-driven exfoliation of graphite into few-layer functionalized Gr nanosheets (nGNSs) was achieved, in which the strong interaction between Nafion (NA) and graphite caused a high yield of 65% under liquid sonication. Due to the surface-protective function of NA, the as-exfoliated nGNSs exhibited good electrical insulation and self-assemble parallelly in the WEP matrix. Electrochemical results confirmed that the nGNSs/WEP coatings displayed extraordinary and durable corrosion protection for carbon steel substrates. With the addition of only 0.3 wt % nGNSs, the corrosion rate of the WEP coatings reduced by 450 times after 120 days of immersion in 3.5 wt % NaCl(aq). Furthermore, scratch experiments clearly verified that the reduced graphene oxide (rGO) had a typical CPA effect but the nGNSs did not. All of these results suggested that the nGNSs provide an appealing approach toward the preparation and application of graphene-based coatings, with great implications for high-performance anticorrosion of WEP coatings.