In this work, passive behaviour and semiconducting properties of AZ80 Mg alloy in phosphate buffer solutions of various pH values ranging from 10.69 to 13.05 were studied. Corrosion and passive current densities measured from potentiodynamic polarization plots, defect density drawn from Mott-Schottky analysis, and finally the resistance and capacitance of the passive films estimated from electrochemical impedance spectroscopy (EIS) were all determined. Potentiodynamic polarization results indicated that increasing pH led to decrease both corrosion and passive current densities. Mott-Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics and the donor densities increased with increasing the pH from 10.69 to 13.05. EIS results showed that the thickness of the passive film increased with increasing the pH. In conclusion, increasing pH values offered better conditions for a thicker passive film formation on AZ80 Mg alloy in phosphate buffer solutions with higher protection behaviour.
