Effect of graphene addition on composition, morphology and corrosion behavior of ZnNiFe-graphene composite coatings

Abstract Graphene reinforced, Zn-rich, Zinc-Nickel-Iron (ZnNiFe-G) coatings were deposited on mild steel substrate by electrolyzing the Zn-Ni-Fe acidic sulphate bath containing different amounts of dispersed graphene layers. Effect of graphene incorporation on composition, microstructure, morphology and electrochemical corrosion performance of coatings was investigated. X-ray diffraction studies revealed ZnNiFe coatings consists η Zn, γ Ni2Zn11 and Fe phases but the concentration of γ Ni2Zn11 phase increased with increasing graphene content in the coating. Incorporation of graphene enhanced the coating compactness and reduced the micro-pores and surface defects. Presence of graphene increased the Ni and Fe content in the coatings. The electrochemical corrosion behavior of the composite coatings was determined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Increase in γ Ni2Zn11 phase concentration, compact and defect free ZnNiFe-G composite coatings exhibited >50% better corrosion resistance performance when compared to the corrosion resistance exhibited by the graphene free Zn-Ni-Fe coating. Among the ZnNiFe-G coatings, the composite coating with combination of highest Ni and graphene content showed the best corrosion resistance performance.