Corrosion behavior of AZ31 magnesium alloy with calcium addition

The effect of calcium on microstructure and corrosion characteristics of AZ31 was investigated. Electron probe microanalysis, scanning electron microscopy and electron back-scattered diffraction were employed for microstructural analysis. Corrosion behavior was characterized by open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy in NaCl at different pH levels. Microstructural observations confirmed the formation of (Mg,Al)2Ca in AZ31–0.5Ca. The corrosion rates were 84.21 mpy/ 31.71 mpy and 23.42 mpy/ 9.40 mpy for AZ31 and AZ31–0.5Ca at pH 6 and pH 11, respectively. Improved corrosion resistance was attributed to segregation of aluminum with calcium to form (Mg,Al)2Ca which reduced β-Mg17-Al12 area fraction.