Corrosion of austenitic stainless steel at 90 °C under highly saline and anoxic conditions: A microspectroscopic study

The stainless steel AISI 309 S used for containers for vitrified high-level radioactive waste was exposed to 90 degrees C under highly saline and anoxic conditions for different exposure times up to 294 days. The surface damage was limited and no pitting could be detected. The corrosion layer is made of an inner-layer mostly of chromium (hydr)oxides and an outer-layer made of Fe-and Ni-based spinel compounds with admixed nickel (hydr)oxides. Minor contributions of magnetite and layered double hydroxide could be identified. Dissolved amounts of metal ions were very low, the pH increased only slightly and the redox potential decrease was limited.

Automated summary

The stainless steel AISI 309 S, used for containers of vitrified high-level radioactive waste, was subjected to 90 degrees C under highly saline and anoxic conditions for different exposure times up to 294 days. The surface damage was minimal, and no pitting was observed. The corrosion layer consisted of an inner layer comprising mostly chromium (hydr)oxides and an outer layer composed of Fe- and Ni-based spinel compounds with admixed nickel (hydr)oxides. Minor amounts of magnetite and layered double hydroxide were also identified. Dissolved metal ion concentrations were very low, with only a slight increase in pH and limited decrease in redox potential.