Study of the corrosion behavior of a 18Cr-oxide dispersion strengthened steel in supercritical water

The corrosion behavior of a 18Cr-ODS (oxide dispersion strengthened) steel exposed in supercritical water (600 °C/25 MPa) was investigated. The results indicate that the weight gain increases with the exposure time, following a parabolic law. A triple layer consisting of an outer layer, an inner layer and a diffusion layer forms on the sample. The phases of the outer layer are Fe2O3 and Fe3O4. The inner layer and the diffusion layer contain (Fe, Cr)3O4 and Cr2O3, respectively. Cracks, pores and exfoliations could be observed on the outer layer. Finally, the oxidation mechanism was discussed and the determining factors were given.

► The corrosion behavior of a 18Cr-ODS steel was investigated.
► A triple oxide layer different from the conventional steels forms.
► The Fe-18Cr/O2 stability diagram is calculated, and oxide mechanism is discussed.
► Reaction rate is also proposed as a rate determining factor.