Optimum amount of graphene oxide for enhanced corrosion resistance by tin-graphene oxide composite coatings

Incorporation of varying amounts of graphene oxide (GO) into conventional Sn coating electrodeposited over mild steel resulted in significant changes in the corrosion resistance performance of the coatings. An aspect of “optimum” GO amount for best corrosion resistance for the Sn-GO composite coatings was explored. All the Sn-GO coatings exhibited compact and crack free morphology. Incorporation of GO facilitated growth along the low index planes and supressed it along the high index planes. Corrosion behaviour of the coatings was examined through potentiodynamic polarisation and electrochemical impedance spectroscopy methods. It was observed that with the addition of GO, the corrosion rate initially decreased to a minimum value and then, upon continued addition of GO, it increased to a value that was even higher than the pure Sn coating. In the case of lower GO amounts, the textured growth coupled with impermeability of GO increased the corrosion resistance whereas, at higher GO concentrations, the galvanic coupling between GO and Sn dominated, leading to lowering of the corrosion resistance.