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 °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. • Stainless steel AISI 309 S was exposed to highly saline anoxic solutions up to 343 days. • The surface attack after 294 days contact time at 90 °C was evaluated. • Synchrotron-based techniques with small beam footprint were applied for analyses. • The corrosion inner-layer consists of chromium (hydr)oxides, corroborated by XPS analysis. • The outer-layer is made of Fe and Ni spinel-type compounds and admixed Ni compounds. [ABSTRACT FROM AUTHOR]