Influence of sulfate ion concentration and pH on the corrosion of Mg-Al-Zn-Mn (GA9) magnesium alloy

The corrosion behavior of Mg-Al-Zn-Mn (GA9) alloy in sodium sulfate solutions was studied over a range of concentrations and solution temperatures at different pH conditions by electrochemical techniques like Tafel extrapolation and electrochemical impedance spectroscopy (EIS). The studies were carried out in solutions with sodium sulfate concentrations 0.1M, 0.5M, 1M, 1.5M and 2M; and at five different temperatures of 30, 35, 40, 45 and 50 °C in a pH range of 3–12. As per the experimental data, the corrosion rate of the alloy increased with the increase in temperature, and also with the increase in concentration of sodium sulfate in the medium. It was observed that the rate of corrosion decreased with the increase in pH. The activation parameters like activation energy, enthalpy of activation and entropy of activation for the corrosion process were calculated. The surface morphology of the alloy was examined before and after corrosion using scanning electron microscopy (SEM).