Comparison of MnCo₂O₄ coated Crofer 22 H, 441, 430 as interconnects for intermediate-temperature solid oxide fuel cell stacks

The low-cost ferritic steel grades 441 and 430 are benchmarked against the specialty grade Crofer 22H as possible interconnect materials for intermediate temperature solid oxide fuel cells. The steels are either pre-oxidized or coated with MnCo2O4. The composition and growth rate of the oxide scales in air is evaluated over a period of 2000 h at 650, 700 and 750 °C. The MnCo2O4 coating is found to reduce the thickness of the oxide scale on all three steels at 700 and 750 °C. The greatest protective effect is achieved on Crofer 22H. A SiO2 scale is formed at the Cr2O3/steel interface after oxidation for all three steels, but it remains discontinuous during the evaluated period. The MnCo2O4 coating provides sufficient protection to make the low-cost steels 441 and 430 promising interconnect materials for operation at 650–700 °C. For higher operation temperatures, 441 is not applicable due to poor scale adhesion.