Characteristic and corrosion studies of rare earth (REE) based anodizing on AZ91D magnesium alloy

Abstract

Oxide coatings on AZ91D magnesium alloy were prepared using anodizing technique with 10mA/cm2 current density for 5 minutes in electrolyte containing Mg (NO₃)₂ with NaVO₃ as an additive. The corrosion behaviors of different coatings condition were evaluated by immersion test in 5.0% NaCl electrolyte for 72 hours. The microstructures were analyzed by Optical Microscope (OM) and Scanning Electron Microscope (SEM). It was found that coatings with the addition of NaVO₃ produced homogeneous primary α-matrix and bigger β-phase (Mg₁₇Al₁₂) compared to untreated AZ91D magnesium alloy. The oxide film formed by anodizing in electrolyte with NaVO₃ enhances the corrosion resistance of the AZ91D magnesium alloy significantly.