Corrosion of metallic interconnects for SOFC in fuel gases

High-temperature alloys can be used to fabricate interconnects for reduced temperature solid-oxide fuel cell (SOFC). These alloys should be neither oxidized nor attacked by carbonaceous gases. Fourteen high-temperature alloys were tested in fuel gases. These alloys were exposed to a simulated SOFC environment. Alloys were attacked by metal dusting in carbonaceous gases of high carbon activity. Pits formed on the alloy surface and grew to large holes through the alloy plate, with subsequent disintegration into a powdery mixture composed of carbon, fine particles of metal, and carbide. The oxide scales on the alloy surface were found to prevent metal dusting corrosion. If the major phase in the oxide scale was chromic oxide, the alloys had good resistance to metal dusting corrosion. However, the alloys were easily attacked if the major phase was spinel. High chromium content in the alloy was helpful to resist metal dusting. The content of spinel in the oxide scales of Ni-base alloys was much less than that in Fe-base alloys. Therefore, the metal dusting rate of Ni-base alloys was lower than that of Fe-base alloys. Alloys were more readily attacked by metal dusting in the high-pressure environment. High humidity retarded metal dusting. (C) 2004 Elsevier B.V All rights reserved.