Effect of Hydrogen Peroxide Concentration on Corrosion Resistance of Cerium-based Conversion Coatings on Mg AZ91D alloy

摘要

The corrosion resistance of cerium-based conversion coatings (CeCCs) on Mg AZ91D alloy was investigated as a function of the hydrogen peroxide (H_2O_2) concentrations in the CeCC spray deposition solution. The corrosion performance of the coated panels was evaluated by ASTM B117 neutral salt spray testing and electrochemical analysis. Coating morphology and thickness were characterized by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES), respectively. All of the panels coated with H_2O_2 in the solution had better corrosion resistance than the 0 vol.% H_2O_2 in solution. Magnesium alloy panels coated with 4 and 8 vol.% of H_2O_2 concentrations in the spray solution performed the best in salt spray tests. Mg AZ91D alloy panels coated with 4 vol.% H_2O_2 had the highest impedance (～12,000 Ω.cm~2), while 0 vol.% peroxide had the lowest impedance (～3000 Ω.cm~2), in agreement with salt spray performance.