Thermodynamic analysis of the simultaneous attack of some metals and alloys by two oxidants

Abstract

The thermodynamic conditions required for the simultaneous attack of metals and alloys by oxygen and another oxidant have been examined. It has been found that oxide scales should usually be formed on the metal surface because of the larger affinity of most metals for oxygen compared to that of other oxidants. However, it has been determined that there are cases where the second oxidant can react with the metal beneath the external oxide scale. These conclusions have been confirmed experimentally by oxidizing pure chromium, Ni 20Cr and Fe 25Cr in air, pure SO 2 and in CO CO 2 mixtures respectively.