Ten iron-based alloys and nickel-based alloys were subjected to oxidation treatment in a hot air environment for various periods. In this investigation, all alloys contained a certain amount of Cr, and Cr2O3 and (Mn,Fe,Cr)(3)O-4 spinel compounds are generated on the surface oxides. Other spinels that contain Cr, Mn, Fe, and Ni are also formed on it; the compositions depend on the composition of the steels and any other materials that are in contact with the interconnects. Accordingly, the role of spinels in the oxidation of interconnects must be understood.