Evaluation of corrosion resistance of coated and uncoated stainless-steel separators at cathode side for molten carbonate fuel cell

In order to evaluate the corrosion resistance of a cathode-side separator for a molten carbonate fuel cell (MCFC), SUS316 and SACC-SUS316 (chromium and aluminum were simultaneously deposited by diffusion into SUS316 austenitic stainless steel substrate using the pack-cementation process) were used as the separator materials. In the case of SUS316, corrosion proceeded via three steps: the formation of a corrosion product until the corrosion product becomes stable; the protection against corrosion until breakaway occurs; and the advancement of corrosion after breakaway. Since SUS316 showed a high corrosion rate in the cathode environment, it would be impossible to use it as a separator without suitable surface modification because of the occurrence of severe stability problems of the cell during long-term operation. In contrast, SACC-SUS316 showed higher corrosion resistance than the present separator material, SUS316. No corrosion was observed on SACC-SUS316 after 480 h at 923 K. Therefore, this material is thought to be very useful as an alternative separator at the cathode side for MCFC in the future.