Reduction of chromium vaporization from SOFC interconnectors by highly effective coatings

The vaporization of Cr-rich volatile species from interconnector materials is a major source of degradation that limits the lifetime of planar SOFC systems with metallic interconnects. In this study, the vaporization of Cr species of a variety high chromium alloys was studied at 800 °C in air using the transpiration method. The measured release of Cr species of the different alloys was correlated with the formed outer oxide scales. A quantitative estimation showed that all the investigated alloys failed to meet the requirements concerning the Cr release from interconnector materials for SOFCs or formed oxide scales which possessed too high electrical resistances. Sputtered ceramic coatings of LSM and LSC and metallic coatings of Co, Ni and Cu were tested with regard to their suitability for Cr retention. The sputtered perovskite coatings turned out to be ineffective in reducing the Cr release to the desired levels. With metallic coatings of Co, Ni or Cu the Cr release could be reduced by more than 99%. The metallic coatings and their oxides effectively reduced the growth of the oxide scale on the steel substrate and showed negligible vaporization rates for Co, Cu and Ni, respectively. Therefore, Co, Ni or Cu were identified as promising and cheap coating materials for metallic interconnectors.