Oxidation/dissolution of ferritic ODS steels in static lead with various oxygen content at 650 °C

• Bi-layer magnetite/spinel scale grows on ferritic ODS steels in Pb with ∼10−3 mass%O at 650 °C.
• Single-layer Cr-based oxide film forms in Pb melt with ∼10−6 mass%O.
• Fine-grained structure of ODS steels favors formation of Cr-based oxide film.
• In pure Pb, the fine-grained structure favors severe dissolution attack.

The compatibility of ferritic oxide dispersion strengthened (ODS) steels with static liquid Pb at 650 °C was investigated for up to 1750 h. The dependence of corrosion behavior on oxygen concentration in the melt and steel structure was determined. The interaction mode changed from intensive oxidation in the oxygen-saturated melt (∼10−3 mass%O), accompanied by the formation of a bi-layer magnetite/spinel scale, to formation of a thin Cr-based oxide film in oxygen-added melt (∼10−6 mass%O) and to the severe steel dissolution in pure Pb (≤10−14 mass%O). The effect of specific phase-structural state of ODS steels (presence of strengthening dispersive oxide particles, fine-grained structure, texture, residual porosity, etc.) on their corrosion response to Pb melts depending on the oxygen concentration is considered. The viability of the in situ formed Cr-based oxide film, as a promising way to improve the corrosion resistance of steels in high-temperature Pb melts (T > 550 °C) is discussed as well.