Corrosion kinetics and mechanisms of 15-15Ti steel in flowing liquid lead-bismuth eutectic at 500°C

The application of Liquid Lead-Bismuth Eutectic (LBE) as a coolant in Lead-cooled Fast Reactors (LFRs) presents significant challenges due to its corrosive nature, especially at elevated temperatures. This study investigates the corrosion kinetics and mechanisms of 15-15Ti stainless steel in flowing LBE at 500 degrees C with oxygen concentrations ranging from 1 to 3 x 10-6-6 wt% and a flow rate of 1 m s-1.-1 . The research highlights the formation and growth of the Fe-Cr spinel oxide layer, which follows a parabolic rate law indicative of a diffusion-controlled process, crucial for long-term material stability predictions. Despite the initial effectiveness of the Fe-Cr spinel layer in mitigating corrosion, its integrity is compromised over time due to spallation and dissolution, allowing penetration of LBE elements and selective dissolution of Fe, Ni, and Cr. The study reveals a complex interplay between direct dissolution of steel components and spallation of the oxide layer, providing critical insights into material loss mechanisms and the degradation of structural materials in LBE-cooled reactors.