Effects of RE (RE = Sc, Y and Nd) concentration on galvanic corrosion of Mg-Al alloy: a theoretical insight from work function and surface energy

Alloying rare earth (RE) elements is an effective method to improve corrosion resistance of Mg-Al alloy but excessive RE concentration may aggravate galvanic corrosion. In this study, density functional theory calculations are performed to unravel effects of RE (RE = Sc, Y, Nd) concentration on the galvanic corrosion of Mg-Al alloy from the perspectives of work function and surface energy. The results showed that, when the RE concentration was low, the galvanic corrosion between Mg matrix and Mg17Al12 phase could be alleviated with the increasing of RE concentration. When the RE concentration was high, the precipitated RE phases became cathodes and strongly aggravated galvanic corrosion of Mg matrix. Furthermore, regardless of the change of RE concentration, the effectiveness of alleviating galvanic corrosion in Mg-Al alloy was in the order: Sc > Y > Nd. Possible explanations to experiments were provided and potential strategy to improve corrosion resistance of Mg-Al alloy was also proposed.