Oxidation behavior of selected FeCr alloys in environments relevant for solid oxide electrolysis applications

Abstract

If society is to move towards using more renewable energy sources the power fluctuations of e.g. wind and solar energy need to be balanced. Energy storage by production of hydrogen from solid oxide electrolysis cells (SOEC) offers a solution to overcome these obstacles. However, the performance of current SOECs decreases too fast for the technology to be commercialized. This drop in performance over time is partly due to the degradation of metallic interconnects (bipolar plates) within the cell stacks. This study investigates the corrosion performance of selected ferritic steels in simulated SOEC environments. Ferritic steels have many properties that are desirable for interconnects but suffer from oxidation and chromium evaporation over time. Four different FeCr alloys have been exposed in different partial pressures of dry O2 (anode side) and in 34% H2O -3% H2-Ar (cathode side) at 850°C and gravimetrical measurements have been performed to study oxidation rates. Chromium evaporation has been measured and compared for the oxygen containing environments. Chromium evaporation was found to vary largely with oxygen partial pressure, while the oxidation rate of the steels did not vary substantially in the different oxygen partial pressures. Differences in oxidation behavior of the steels were observed between the exposures in different partial pressures of dry O2 and in 34% H2O -3% H2 -Ar. Both reduced and increased oxidation rates were observed in the steam with hydrogen environment compared to the oxygen environments for different materials. Keywords: Solid oxide electrolysis cell, SOEC, SOFC, degradation, high temperature corrosion, chromium evaporation, denuder technique