Synergistic effect of nickel and oxygen on 316L stainless steel corrosion in liquid lead

Austenitic 316L suffers dissolution corrosion in liquid lead (Pb) as the selective leaching of nickel (Ni) results in a destabilized microstructure. We demonstrate a chemistry-based corrosion control approach in which sub-saturated Ni together with controlled oxygen additions co-inhibit dissolution and promote oxide formation. Tests at 500 °C for 500 h spanned a 2 × 3 matrix (Oxygen: 5 · 10 ^–8 and 5 · 10 ^–7 wt.%; Ni: 0, 0.05, 0.1 wt.%). In-situ oxygen concentration and oxygen consumption monitoring, corrosion depth measurements, and microstructure measured by SEM/EDX were assessed. In Ni-free lead, uniform selective leaching of Ni from the stainless steel is observed. At 0.05 wt.% dissolved Ni the depth of dissolution is localized and reduced by a factor of 10. And with 0.1 wt.% Ni, oxidation of the steel dominated at both oxygen concentrations. Oxygen consumption at 5 · 10 ^–7 wt.% was ∼3 times that at 5 · 10 ^–8 wt.%, consistent with ∼3 times thicker oxide. This work indicates a coupled effect of dissolved Ni and O that reduces dissolution corrosion observed on stainless steel in high temperature lead.