Nanoscale study on the roles of sensitization in corrosion of 316H SS in liquid lead bismuth environments

• Intergranular and intragranular corrosion are observed on all the 316H samples. • The Ni-Fe phase can inhibit the diffusion of oxygen and Fe in 316H. • Degree of sensitization has a weak correlation with corrosion resistance. Austenitic stainless steel (SS) is one of the most promising structural materials for once through steam generator (OTSG) of lead-cooled fast reactors (LFR). In this article, 316H SS samples with different degrees of sensitization were subjected to corrosion experiments in a liquid lead-bismuth environment at 550°C for 1000 h. Intergranular and intragranular oxidation were observed in all samples, but the degree of sensitization had a weak correlation with the oxide thickness of 316H SS in the LBE environment. The presence of a micron-scale/nm-scale Ni-Fe phase at grain boundaries and in grains was verified by transmission electron microscopy and atom probe tomography, which inhibited the inward diffusion of oxygen and outward diffusion of Fe in 316H SS and impeded oxidation front.