Evaluation of protective coatings for SOFC interconnects

Chromium poisoning is a widely recognized degradation process in solid oxide fuel cells (SOFC). Stainless steel interconnect plates, in direct contact with the cathode, have been identified as the major chromium source, raising a need for electrically conducting protective coatings for the interconnects. This work evaluates four different manganese-cobalt protective coatings manufactured on thin steel foils, made by three commercial companies and a research centre. Area specific resistance, coating microstructure, and chromium retention are compared. Measurements were done in a humid atmosphere over 1000 hours at 700 °C. An innovative measurement setup was used, in which the coated steel samples are stacked adjacent to thin palladium foils with a screen-printed lanthanum strontium cobalt layer, replicating an SOFC cathode. As a conclusion, TeerCoating Ltd's and Turbocoating S.p. A's coatings performed similar to the Sandvik Material Technology's cerium-cobalt reference coating, and could be employed as such in SOFC applications.