Oxidation behavior of coated and preoxidized ferritic steel in single and dual atmosphere exposures at 800 °C

Ferritic stainless steel (FSS) is commonly used for interconnects in planar solid oxide fuel cell (SOFC) stacks. Interconnects separate and connect individual cells into a stack and are simultaneously subjected to air on the cathode side and fuel on the anode side, creating a “dual atmosphere” exposure. In this study, the surface morphology and chemistry of CoMn coated FSS (Crofer 22APU) samples (with and without pre-oxidation for 100 h in 800 °C laboratory air) were analyzed as a function of exposure to single atmosphere (moist air) and dual atmosphere environments (moist air/moist hydrogen) for 200 h at 800 °C. Thin film (~ 2 μm) CoMn coatings were deposited via magnetron sputtering on as-received and pre-oxidized samples. Pre-oxidation significantly inhibited outward iron transport from the FSS to the surface and reduced overall surface oxide layer thickness both for uncoated and CoMn coated samples . The observed oxidation behavior and surface layer evolution in both single and dual atmosphere are presented and correlated with possible transport mechanisms.