Comparison of Ce/Co and Ce/FeNi coatings for interconnects in solid oxide electrolysis

Manganese Cobalt oxide (MCO) coatings have been extensively studied for interconnect applications in solid oxide fuel cells (SOFC). Nevertheless, Co is a critical raw material and efforts are taken to replace it. Ce/FeNi coatings are proposed as an alternative and compared to Ce/Co on AISI 441. Chromium evaporation behaviour, oxidation kinetics, interfacial fracture energy, and area-specific resistance (ASR) of the coating and steels were investigated for up to 3,850 h at 850 °C. Ce/FeNi coatings were not found to be as effective as Ce/Co coatings in preventing chromium evaporation. Nevertheless, Ce/FeNi coated steels showed 50 % lower parabolic rate constant and ASR than Ce/Co coated steel. Additionally, the fracture energy of the adherence of the Ce/FeNi coating to the steel was measured at 750 and 850 °C. The Ce/FeNi coating adherence to the steel greatly outperformed the Ce/Co coating adherence. Furthermore, while the fracture energy of the Ce/Co coating decreases with exposure time, it increases over time for the Ce/FeNi coating. • Ce/FeNi- and Ce/Co-coated AISI 441 were investigated for up to 3,850 h at 850 °C. • Ce/FeNi coated steel exhibits higher Cr(VI) evaporation but a lower oxidation rate. • ASR measurements for Ce/FeNi coated steel were almost 50 % lower than Ce/Co. • Ce/FeNi coated steel had higher fracture toughness than Ce/Co.