Poly(m-phenylenediamine) encapsulated graphene for enhancing corrosion protection performance of epoxy coatings

Graphene (G) is regarded as a tremendous potential corrosion protection material owing to its perfect impermeability. However, the tendency of graphene nanosheets to agglomerate and the corrosion-promotion effect brought by its native high electrical conductivity seriously affect its anti-corrosion application. In this paper, high-energy ball milling was used to prepare graphene with excellent impermeability. Then, insulating poly(m-phenylenediamine) encapsulated graphene (G@PmPD, conductivity of 1.2 × 10^-7S cm^-1) was prepared through non-covalentπ-πinteraction. The resulting amino-rich G@PmPD exhibits stable dispersibility and excellent compatibility in organic solvents and polymer matrix. Embedding 0.5 wt% of G@PmPD into the epoxy matrix, and the composite coating can effectively protect the steel substrate for up to 60 d. This superior corrosion resistance is attributed to the impermeability inherited by G@PmPD and the compactness improved by the cross-linking of G@PmPD and EP. Especially in the damaged state, the composite coating embedded with low conductivity G@PmPD triumphantly eliminated graphene's corrosion-promotion effect. This study provides promising inspiration for the application of graphene in anti-corrosion field.