Corrosion resistance and microstructure characterization of rare-earth-transition metal–aluminum–magnesium alloys

This paper reports the results of investigation carried out to evaluate the corrosion resistance and microstructure of some cast alloys represented by the general formula: La0.7−xPrxMg0.3Al0.3Mn0.4Co0.5Ni3.8 (x = 0, 0.1, 0.3, 0.5, and 0.7). Scanning electron microscopy (SEM) and electrochemical methods, specifically, polarization curves and electrochemical impedance spectroscopy (EIS), have been employed in this study. The effects of Pr substitution on the composition of the various phases in the alloys and their corrosion resistance have been studied. The electrochemical results showed that the alloy without Pr and the one with total La substitution showed the highest corrosion resistance among the studied alloys. The corrosion resistance of the alloys decreased when Pr was present in the lowest concentrations (0.1 and 0.3), but for higher Pr concentrations (0.5 and 0.7), the corrosion resistance increased. Corrosion occurred preferentially in a Mg-rich phase.