Corrosion of pre-oxidized austenitic stainless steel 316L in stagnant lead-bismuth eutectic containing 10 wt.% oxygen at 803K

Watanabe, Nao  ; Irisawa, Eriko ; Kato, Chiaki   

Oxide layers form at a surface of 316L stainless steel (SS) in lead-bismuth eutectic (LBE) with sufficient oxygen concentration. The oxide layers are known to suppress dissolution corrosion of SS in LBE under constant conditions. However, it was unclear how well the corrosion suppression effect of the oxide layers formed in LBE would be maintained when it exposed to a reducing atmosphere. In order to evaluate it, a reduction test of pre-oxidized 316L SS in stagnant LBE at 803K and low oxygen concentration from 10 wt.% to 10 wt.% for 1976h was performed. After pre-oxidation, an outer FeO layer and an inner Fe-Cr oxide layer formed at the surface of 316L SS. After the reduction test, most of FeO layer was dissolved. On the other hand, Fe-Cr oxide layer was not, and the Fe-Cr oxide layer without Ni prevented LBE penetration. However, the Fe-Cr oxide layer cracking in some areas was observed and LBE penetrated through the layer there.