The oxidation behavior of alloy 625 and 120 foils was studied at 650, 700 and 800 ∘C in dry air and flowing air + 10% H2O up to 10,000 h (alloy 625) or 30,000 h (alloy 120). The effect of water vapor on Cr loss was investigated. Manganese and iron in the 120 foil induced faster Cr depletion in the foil and breakdown of the Cr2O3 scale into Fe and Cr-rich oxide compared to the alloy 625 foil. In the latter case, the presence of Nb led to the formation of Nb and Cr-rich oxide after breakdown of the Cr2O3 scale. Simultaneous Cr loss due to oxidation and volatilization of the Cr2O3 oxide scale was predicted and compared to experimental Cr loss measurements for exposures up to 30,000 h.