Mechanism of corrosion of 9Cr and 12Cr ferritic/martensitic steels under oxygen-saturated sodium

Highlights: • Ferritic/martensitic steels (Gr.92 and HT9) were exposed to oxygen-saturated Na. • Tests were carried out at 650 °C and 550 °C for 300 h. • Na-Cr-O compound formed in the matrix of Gr. 92 and HT9 samples. • Gr. 92 has a higher corrosion rate than HT9 in oxygen-saturated Na. • In oxygen-saturation Na, corrosion is very rapid than the reported values. - Abstract: Liquid sodium corrosion poses a major problem with liquid-sodium-cooled fast reactors. Ferritic/martensitic steels are used as cladding materials and structural materials in these reactors. Gr.92 and HT9 steels were exposed to oxygen-saturated sodium at 650 °C and 550 °C for 300 h, and a Na-Cr-O compound formed in the matrix of specimens. Gr.92 showed a higher corrosion rate than HT9. The corrosion rate of Ferritic/Martensitic Steels (FMS) in oxygen-saturated sodium was also modelled in this study. The empirical model was compared with the short-term experimental data. The results show that the empirical model had close value to the short-term experimental model.