High corrosion resistance of metal-graphene oxide-metal multilayer coatings

Attributes such as chemical inertness and impermeability make graphene and graphene oxide (GO) ideal materials for corrosion protection coatings. This work shows the application of chemically synthesised GO for corrosion protection by sandwiching it within metallic coatings to form a metal-GO-metal multilayer geometry. Two different multilayer systems were investigated: SnZn–GO–SnZn and ZnNi–GO–ZnNi multilayer coatings. Metallic coating was electrodeposited on mild steel. Followed by drop casting of as-synthesised GO over the metal deposit. The final metal layer was then electrodeposited over the drop casted GO. A control experiment was conducted by decreasing the thickness of the top metal in order to bring the GO nearer to the exposed surface. For both the systems, one pristine coating and three different multilayer coatings were electrodeposited. Total time of metal deposition was kept constant for all the coatings. Corrosion resistance of the coatings was investigated in 3 wt% NaCl solution by potentiodynamic polarisation and electrochemical impedance spectroscopy methods. The corrosion measurements clearly showed that the corrosion resistance of all the multilayer coatings was greater than the pristine metallic coating and between the multilayer coatings, as the thickness of the top metal layer decreased thereby causing the GO layer to advance towards the surface facing the corrosive medium the corrosion resistance of the multilayer coating increased. This study clearly illustrates the effect of inertness and impermeable of GO in protecting the underlying substrate against corrosion reaction.