An approximate calculation of the oxygen activity profile in solid-solution scales formed during the oxidation of binary alloys

A simplified method to calculate the oxygen activity profiles in solid-solution scales formed on binary alloys is proposed. This is based on Wagner's theoretical analysis but involves the solution of a single first-order differential equation by a process of successive approximations using the experimental data on the profiles of the scale composition. The agreement between the oxygen activity profiles calculated by this procedure and those obtained by the more general treatment is satisfactory for the systems examined. The method can therefore be used to obtain rapidly an approximate oxygen activity profile when the conditions for the application of the theory are satisfied.