A molecular dynamics study on anticorrosion properties of graphene/epoxy nanocomposites in NaCl medium

This work aims evaluate the role of graphene derivatives in epoxy coatings. We proposed new models composed of iron, graphene derivative/epoxy composites and a corrosion medium (NaCl), and evaluated the effects of the graphene derivatives in the epoxy coatings on the corrosion of iron by using Molecular Dynamics (MD) and Density Functional Theory (DFT). We used graphene derivatives such as pristine graphene (PG), graphene oxide (GO), reduced graphene oxide (RGO), and functionalized graphene oxide (FGO, where F represents two forms of nitrogen-based groups, which are amine -NH₂ and amide -C([double bond, length as m-dash]O)-NH₂), and also modeled pure epoxy coatings for comparison. The interaction energy between the graphene derivatives and epoxy resin increased in the order of PG, GO, RGO and FGO, and the interaction energy between the epoxy coating layer and the iron layer was rather larger than that of coatings with graphene derivatives. Interestingly, during the simulation, the interaction energy between the pure epoxy coating and the iron was reduced compared to that of the epoxy coating with GO, RGO and FGO. The wear of the coatings during the simulation was low for the coatings with PG and FGO, although the coatings with GO and RGO showed more severe wear than the pure epoxy coating. Finally, the permeation coefficient of the coatings was calculated. It was largest with PG, and reduced in the order of RGO, FGO and GO in the composite epoxy coatings. The results showed graphene derivative/epoxy composites had significantly better corrosion resistance than pure epoxy; in particular, the epoxy resin composite with GO represented the best corrosion resistance. This study may be important for developing graphene-reinforced plastic composites with good anticorrosion properties.