The kinetics of growth and the critical conditions for the formation of the most-stable oxide in the oxidation of binary alloys

During the growth of the most-stable oxide BO_v in the oxidation of binary alloys containing nonnoble components A and B, the oxygen pressure prevailing at the alloy-scale interface is higher than the corresponding value for equilibrium between BO_v and pure B. The effects of this change on the rate constant for the growth of BO_v and on the critical concentration of B in the bulk alloy required for the stability of BO_v on its surface are examined and discussed. The general treatment is then applied to the growth of NiO on Cu–Ni alloys and of Cr₂O₃ on Fe–Cr, Co–Cr, and Ni–Cr alloys by using appropriate defect models for these oxides, considering also the possibility of oxide doping.