Review of Recent Developments in the Formulation of Graphene-Based Coatings for the Corrosion Protection of Metals and Alloys

Corrosion is a naturally occurring phenomenon and there is continuous interest in the development of new and more protective coatings or films that can be employed to prevent or minimise corrosion. In this review the corrosion protection afforded by two-dimensional graphene is described and discussed. Following a short introduction to corrosion, the application of graphene in the formulation of coatings and films is introduced. Initially, reduced graphene oxide (rGO) and metallic like graphene layers are reviewed, highlighting the issues with galvanic corrosion. Then the more successful graphene oxide (GO), functionalised GO and polymer grafted GO-modified coatings are introduced, where the functionalisation and grafting are tailored to optimise dispersion of graphene fillers. This is followed by rGO coupled with zinc rich coatings or conducting polymers, GO combined with sol-gels, layered double hydroxides or metal organic frameworks as protective coatings, where again the dispersion of the graphene sheets becomes important in the design of protective coatings. The role of graphene in the photocathodic protection of metals and alloys is briefly introduced, while graphene-like emerging materials, such as hexagonal boron nitride, h-BN, and graphitic carbon nitride, g-C3N4, are then highlighted.