Effect of Graphene Oxide as an Anodizing Additive for the ZK60A Magnesium Alloy: Correlating Corrosion Resistance, Surface Chemistry and Film Morphology

Abstract

The aim of the present work was to study the effect of graphene oxide as an additive in the anodization bath of the ZK60A magnesium alloy on the corrosion resistance, film morphology and surface chemical composition. The anodizing process was conducted at a constant current density of 30 mA.cm−2 in an electrolyte consisting of 3 M de KOH, 0.15 M de Na2SiO3 and 0.1 M Na2B4O7.10H2O. Graphene oxide was added to this bath at three different concentrations: 0.5 g.L−1, 1.0 g.L−1 and 3.0 g.L−1. The ability of the graphene oxide nanofiller to enhance the corrosion resistance of the ZK60A alloy was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. The surface chemical composition was assessed by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) coupled with EDS analysis was employed to examine the anodized layer morphology and thickness. The results pointed to a beneficial effect of graphene oxide addition on the corrosion resistance of the anodized ZK60A which was dependent on the concentration of the nanofiller in the anodizing electrolyte.