First-principles modeling of corrosion current for passive magnesium alloys and its application in Mg-RE alloy

Abstract

Theoretical calculation could simulate Mg alloy corrosion behavior from electrochemical thermodynamic factors. By considering the kinetic factor as the passivation oxide layer, a comprehensive corrosion current model has been set up in this work. The corrosion current modeling should belgJtot′=lgJa+∆lgJc+km×∑fm×∆Em+ki×∑(fi×∆Ei)−koxCPBR×Winterface−∆Gs−∆GF(ln10)RT)). The formula as koxCPBR×Winterface−∆Gs−∆GF(ln10)RT) is just for passivation factor. Alloying element segregation energy ∆Gs, oxide formation energy ∆GF, oxide PBR value CPBR, interface cleavage work Winterface have all been considered. By this more considerate modeling, the corrosion current lgJtot′ (related to polarization icorr) could be obtained for passivate Mg alloys such as Mg-RE series (RE =Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). Moreover, the prediction is quite coherent to experimental electrochemical polarization result. The work provides a more precisely prediction for Mg alloy with passivation. It also proposes a passivation criterion for seeking corrosion-resistant Mg alloy in another way.