EIS study and role of chloride ions concentration and temperature on passivity of AZ91D Mg alloy

Abstract

Mg alloy shows higher specific strength and ductility relative to aluminum and also lower machining and casting costs over to steels. However, it also shows limitation to use in many industrial applications due to the relatively poor corrosion resistance in many aqueous solutions. Corrosion and passivation study of magnesium alloy (AZ91D) in various Cl� ions concentrations and temperatures were carried out using electrochemical impedance spectroscopy (EIS) in NaCl solutions of 0.4, 0.6, 0.8 & 1.0 molar (M) concentrations. The passivation behavior was also observed at temperature of 45�C, 55�C and 65 �C in 3.5 wt% NaCl solutions. The total polarization resistance was observed about 5530, 4030, 2465 and 2000 Ohms.cm2 in solutions of 0.4, 0.6, 0.8 & 1.0 M NaCl respectively indicate reduction of film stability at higher chlorides concentration. A similar trend was found on increasing temperatures of 3.5 wt% NaCl solutions at 45�C, 55�C and 65 �C and noticed about 970, 600 and 300 Ohms.cm2 respectively showed significant decline of passivity and more pitting tendency. � (2015) Trans Tech Publications, Switzerland.