The influence of pre-treatment on the oxidation behavior of Co coated SOFC interconnects

Cobalt coatings are candidates to inhibit high-temperature surface oxidation of solid oxide fuel cell (SOFC) stainless steel (SS) interconnects. This study investigates the influence of surface pre-treatment on the oxidation behavior of cobalt coated SS441. Metallic cobalt was deposited via DC magnetron sputtering on SS that had been pre-oxidized for 0, 10, and 100 hrs in 800 °C air. The samples were analyzed using FE-SEM/EDX, XRD, and XPS before and after 10 and 100 h of oxidation. Significant differences in oxidation behavior were observed. For example, the pre-oxidized samples exhibited combined coating/oxide scales that contained much less Fe and were significantly thinner compared to samples that were not pre-oxidized. The presence of a continuous chromium oxide layer (from pre-oxidation) may inhibit iron transport from the substrate and thus reduce the thickness of the oxide scale. Possible mechanisms for the observed oxidation behavior are presented and discussed.