Electrochemical corrosion behaviour of binary magnesium - heavy rare earth alloys

The corrosion properties of magnesium-heavy rare earth (RE) based alloys have been studied. Binary additions of gadolinium (Gd), dysprosium (Dy) and erbium (Er) to pure magnesium were made to a nominal 1 at.%. The corrosion resistance of Mg99Gd1, Mg99Dy1 and Mg99Er1 alloys has been assessed by using open circuit potential measurements, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) carried out in 0.075 M Na2B4O7 + 0.05 M H3BO3 solution, pH = 8.4. Electrochemical results showed that heavy RE alloying additions significantly improves the corrosion behaviour of magnesium. This improvement can be attributed to enhanced barrier properties of the corrosion products layer and additional active corrosion protection originated from the inhibiting action of the lanthanide cations entrapped as oxides/hydroxides in this surface layer.