Oxidation of Porous Stainless Steel Supports for Metal-Supported Solid Oxide Electrolysis Cells
Oxidation behavior of porous P434L ferritic stainless steel, used for the fabrication of metal-supported solid oxide electrolysis cells (MS-SOEC), is studied under oxygen-side and steam-side conditions. The impact of oxygen content on the oxygen side and steam:hydrogen ratio on the steam side is determined at 700 °C for bare, as-sintered samples. For these conditions, oxidation is more aggressive in the steam-side atmosphere. Oxygen with 3% humidification and steam:hydrogen ratio of 90:10 are selected for further assessment with pre-oxidized, catalyst-coated, and CuMn1.8O4-coated samples. The rapid oxidation at 700 °C and breakaway oxidation at 600 °C observed for bare stainless steel in 90:10 steam:hydrogen is mitigated by pre-oxidizing the sample in air before exposure. In oxygen, addition of the catalyst or CuMn1.8O4 coatings moderately increases the oxidation rate, due to consumption of Cr via reaction between the coatings and Cr-oxide scale. The results for ex-situ controlled oxidation are similar to oxidation observed after 1000 h operation of a full MS-SOEC. In general, the oxidation behavior at 700°C is found to be acceptable.