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 ?m) 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. © 2011 Elsevier B.V.