Corrosion resistance of oxide scales formed in high-temperature oxidation of Al-bearing ferritic stainless steel

Electrochemical polarization measurements were performed on Albearing stainless steels covered with oxide scales formed at 973, 1173, and 1373 K, and the pinhole defect density and the reductive dissolution behaviors of the scales were investigated. The increase of oxidation temperature and the content of Al led to the growth of a thick Al-rich oxide scale. The Al-rich oxide scales had less pinhole defects, resulting in high corrosion resistance in acidic condition. In contrast, Fe-rich oxide layers formed at lower oxidation temperatures dissolved cathodically. The Al addition was effective to decrease the pinhole defects and to enhance the corrosion resistance of the oxide scales due to the formation of the Al-rich oxide scale.