Improving mechanical properties and corrosion resistance of AZ31 alloy by micro-arc oxidization and post supercritical CO2-assisted electroless plating

Abstract

Anti -corrosion and wear resistance of AZ31 alloy were enhanced through a three -stage surface treatment, which comprised surface micro -arc oxidation (MAO), sputtering and post supercritical CO2-assisted electroless plating (PSC-CO2-EP). In the MAO treatment, attempts were made to vary the F ion content in the electrolyte to investigate its impact on the morphology and composition of the oxide film. Subsequently, the MAO -treated AZ31 alloy underwent Ag sputtering, followed by the preparation of the Ni coating using the PSC-CO2-EP method (PSC-CO2-Ni). The SEM micrographs indicate that the addition of F ions to the electrolyte effectively improved the uniformity, thickness and compactness of the MAO -generated oxide film. Further modification with the sputtered Ag layer could enhance the adhesion between the Ni coating and the as -prepared oxide film. Additionally, the application of SC-CO2, with high diffusivity and low surface tension, significantly improved the anti -corrosion and wear resistance of the AZ31 alloy surface even after pressure release. The results demonstrate that the multilayer design proposed in this study addresses the vulnerability of the AZ31 alloy surface to corrosion. Furthermore, compared to the SC-CO2-assisted plating method, the PSC-CO2-EP technique offers greater process flexibility and exhibits high potential for practical applications.