Oxidation of MnCu0.5Co1.5O4 spinel coated SUS430 alloy interconnect in anode and cathode atmospheres for intermediate temperature solid oxide fuel cell

In order to improve the performance of SUS 430 alloy as a metallic interconnect material for intermediate-temperature solid oxide fuel cell (IT-SOFC), a low-cost and Cr-free spinel coating of MnCu0.5Co1.5O4 on SUS430 alloy substrate by sol-gel method is studied. MnCu0.5Co1.5O4 coated SUS430 alloy is evaluated in the simulated reducing (anode) and oxidizing (cathode) SOFC working environments at 750 °C for 1000 h about the microstructure, oxidation resistance and electrical conductivity. The result confirms that the spinel coating shows electrical conductivity of 105.5 S cm−1 at 750 °C in air and an average CET value of 12.27 × 10−6 K−1 at temperature range of 20-1000 °C. The coating layer is identified as MnCu0.5Co1.5O4 in cathode, and MnO, Cu and Co in anode atmosphere. And the thickness of the oxidized scale is around 7-8 μm after 1000 h of oxidation in both situations. The dense coating layer is effective in blocking the Cr migration/transport and depressing the growth of Cr2O3 and formation of MnCr2O4. In cathode atmosphere, the oxidation kinetics obeys the parabolic law with a rate constant as low as 1.77 × 10−15 g2 cm−4 s−1 and the ASR contributed by the oxide scale is 0.3 mΩ cm2. In anode atmosphere, the Δm/A of MnCu0.5Co1.5O4 coated SUS430 alloy is 0.2 mg cm−2 for 1000 h. Generally, the overall performance of the MnCu0.5Co1.5O4 coated SUS430 alloy is superior to those of bare SUS430 and other ferritic candidate alloys.