Effect of pre-oxidation on the corrosion behavior of Al-containing ODS steel in oxygen- saturated static LBE at 600 and 700°C

Abstract

The corrosion behavior of an Al-containing oxide dispersion strengthened (ODS) steel at 600 and 700°C oxygen-saturated static Pb-Bi eutectic was investigated with and without a pre-oxidation heat treatment. Without pre-oxidation, the ODS steel formed a multilayer oxide scale consisting of outer Pb-Fe-O/magnetite and inner Fe-Cr-Al spinel/Cr(Al)-rich film on the surface during the corrosion exposure at 600°C up to 3100 h. In contrast, the pre-oxidized ODS samples was covered by a thin, dense and continuous pre-formed Al₂O₃ scale, which effectively improved the corrosion resistance. Although the Al₂O₃ scale was gradually reacted with Pb-O clusters to form Pb-Al-O compound with the prolonged exposure time to 3100 h, the total thickness of oxide layers was still less than about 1 μm. Exposed to elevated temperature of 700 °C, the corrosion mode changed significantly. Both ODS samples spontaneously formed an external Al₂O₃ during the exposure for 100 h. However, with prolonged exposure time to 500 h at 700 °C, the integrity of the protective Al₂O₃ scale gradually destructed. Small nodule-like oxides emerged from localized areas in the pre-oxidized samples, while more thicker oxide layer was form in the as-received samples. which intensified corrosion by the aggressive LBE melt. The results suggest that optimized pre-oxidation treatment can effectively to improve the corrosion resistance of Al-containing ODS steel.