Improved Assessment of Chromium Evaporation Rates in Solid Oxide Cell Balance of Plant Component Alloys

The chromium (Cr) evaporation from balance-of-plant (BoP) component alloys in high-temperature environments can severely deteriorate the electrochemical performance of solid oxide cells (SOCs) in fuel (SOFC) and electrolysis (SOEC) modes. However, accurate assessment of Cr evaporation is challenging due to potential interferences from the experimental conditions and test apparatus. In this study, we investigate four distinct methods for assessing the Cr evaporation rates of candidate alumina-forming austenitic and chromia-forming austenitic BoP alloys under relevant simulated SOC operating conditions of 800-900 degrees C in air with 10% H2O. A method using a sodium carbonate coated thin alumina tube is identified, which effectively mitigates the interference caused by (1) the deposition of silicon deposits originating from quartz furnace tubes, (2) detrimental effects of sodium species on the oxidation process of alloys from the sodium carbonate used to enhance Cr oxy hydroxide species capture, or (3) chemical interaction between Cr gaseous species and the alumina furnace tube. This optimal method provides improved assessment of Cr evaporation, enabling further efforts to build correlation between Cr species quantities to the degradation rates of SOCs.