THE TRANSIENT STATE IN THE OXIDATION OF BINARY-ALLOYS FORMING THE MOST-STABLE OXIDE - A NUMERICAL-SOLUTION

The initial transient high-temperature oxidation stage for binary allo ys forming the most-stable oxide has been examined by means of a numer ical procedure based on the finite-difference method. At variance with previous models, the present treatment takes into account the effect of the rate of the reaction at the scale/gas interface over the corros ion kinetics. The calculations concerning the transient stage are deve loped either using the rate of the reaction at the scale/gas interface as a boundary condition without imposing any particular rate law to t he overall process. A correct analysis of the oxidation behaviour of b inary alloys during alloys during the transient stage must take into a ccount the kinetics effect of the rate of the surface reaction. The co ncentration of the most-reactive element at the alloy/scale interface changes regularly with time, decreasing gradually from the initial bul k value to its final steady-state value. The present results are in go od agreement with those obtained by means of an approximate analytical model developed previosly.