High-Temperature Corrosion Behavior of Fe-18Ni-12Cr-2.9Al and Fe-18Ni-12Cr-2.3Al-Nb-C Austenitic Steels Depending on Dissolved Oxygen Concentration in Static Liquid Pb at 700 °C

The corrosion behavior of the aluminum-alloyed austenitic steels Fe-18Ni-12Cr-2.9Al and Fe-18Ni-12Cr-2.3Al-Nb-C was investigated at 700 °C in static Pb for 1000 h as a function of the concentration of dissolved oxygen in the liquid metal. In Pb with ~ 5 × 10–9 mass % dissolved oxygen, both steels showed dissolution. Depth of corrosion averaged 67 (± 18) µm and 78 (± 25) µm for Fe-18Ni-12Cr-2.3Al-Nb-C and Fe-18Ni-12Cr-2.9Al, respectively. In Pb with higher oxidation potential of 2 × 10–6 mass %O, both steels showed protective and accelerated oxidation. The protective thin oxide film (≤ 1 µm) was composed of outermost Fe-rich, intermediate Cr-rich and inner Al-rich sublayers. The thicker oxide scale was of irregular thickness (2 ÷ 30 µm) and consisted of Fe–Cr mixed oxide with Ni-rich metallic inclusions.