Corrosion rate determination of rare-earth Mg alloys in a Na2SO4 solution by electrochemical measurements and inductive coupled plasma-optical emission spectroscopy

The corrosion resistance of three Mg alloys containing rare-earth elements (WE43, EV31 and ZE41) was studied and compared to that of two Mg– Al alloys (AZ31 and AZ91) and of pure Mg (99.95 wt.%). Current-voltage curves and electrochemical impedance measurements were performed with rotating disk electrodes in an aerated 0.1 M Na2SO4 solution. For all the alloys, it was confirmed that the intermetallic particles acted as local cathodes and that more protective films were formed on the alloys surface by comparison with the pure Mg. Corrosion rates were determined from inductive coupled plasma-optical emission spectroscopy measurements and from the electrochemical measurements. Higher corrosion rates were observed for the rare-earth Mg alloys compared to the AZ series alloys. These data allowed the corrosion mechanisms to be discussed.