Abstract
Literature within the past two decades has highlighted the ongoing issue of dual atmosphere corrosion in solid oxide fuel cell (SOFC) systems. This corrosion phenomenon occurs as a result of simultaneous exposure of ferritic stainless steel interconnects to the anodic fuel gas on one side and cathodic air stream on the opposing side. In this, the air-exposed side of the metal interconnect undergoes fast, anomalous corrosion and metal loss in the form of iron oxide overgrowth with whisker and platelet-type morphology. Studies have indicated that the corrosion is favored at lower temperatures in comparison to temperatures above 800 °C. This poses an issue for the current trend of lowering SOFC operating temperatures and utilizing cost-effective ferritic stainless steels as interconnect materials. In this study, the oxidation behavior of two ferritic stainless steels is examined under dual atmosphere exposure conditions. A series of experiments with varying time, temperature, and steel compositions were carried out to better understand the effects of these variables on severity and morphology of corrosion products. A mechanism which describes the localized overgrowth of iron oxide in platelet and whisker form and the porous oxide sub-layer is proposed. The transition from a thin, protective, and dense chromia scale under nominal ambient conditions to porous, non-protective scaling under dual atmosphere conditions will be discussed.
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