Effect of aluminum and zinc on the corrosion behavior of AZ (Mg-Al-Zn) series magnesium alloys

Abstract

The microstructures and corrosion behaviors of AZ series magnesium alloys (AZ31, AZ61, AZ91, AZ62, and AZ63) were investigated via materials characterization, immersion, and electrochemical tests. Both Al and Zn can promote the corrosion of magnesium alloys via promoting the segregations of β-Mg₁₇Al₁₂ and eutectic α phases, respectively. AZ63 magnesium alloy performs the highest corrosion rate due to the high amount of eutectic α phases, which facilitates the desorption of corrosion products. The area ratio of products free region on the electrode surface and activity of univalent Mg ion (C_Mg+) as two state variables, which would give rise to capacitive and inductive responses in electrochemical impedance spectroscopy responses, were interpreted by the kinetics of electrode process, respectively.