Degradation of Ferritic Steel Interconnects in SOEC Environments

Abstract

This study investigates the corrosion performance of selected ferritic steels in simulated solid oxide electrolysis cell (SOEC) environments for exposure times up 500 h. 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 concentrations 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 dry O2 and in 34% H2O -3% H2 -Ar. Both reduced and increased oxidation rates were observed in the cathode side atmosphere compared to the oxygen side atmosphere for different materials.

High Temperature Electrolysis in Alkaline Cells, Solid Proton Conducting Cells, and Solid Oxide Cells

“…Testing has been conducted at various scales, including stack modules consisting of up to two 60-cell stacks . As a part of a demonstration project, the produced synthesis gas was fed through a Fischer–Tropsch reactor to produce liquid hydrocarbon fuels. , In general the stacks are found both to perform worse and also to degrade faster than single cells due to chromium deposition from the interconnects and due to thermal imbalance. , It is general accepted that the stack components may have a negative influence on the cell/stack degradation due to interconnected oxidation, deposition of impurities, as well as contact losses. ,,− …”

Chromium deposition and poisoning at La0.6Sr0.4Co0.2Fe0.8O3−δ oxygen electrodes of solid oxide electrolysis cells

“…17 Under the operation conditions of SOECs, gaseous Cr species such as CrO 3 and CrO 2 (OH) 2 would be generated from the oxidation of chromium oxide scale of the interconnect. 18,19 The mechanism and kinetics of the deposition and poisoning of the Cr species at LSM and LSCF cathodes under the operation conditions of SOFCs has been extensively investigated. 20,21 For the O 2 reduction reaction on the LSCF cathode, the Cr deposition occurs preferentially on the outer surface of the electrode rather than at the electrode/electrolyte interface region.…”

Thermal Sprayed Protective Coatings for Bipolar Plates of Hydrogen Fuel Cells and Water Electrolysis Cells

“…As mentioned in 2.2, high-temperature oxidation of the FSS BPs mainly occurs on the SOFC-cathode and SOEC-anode sides [86]. Although both cases are exposed to oxygencontaining gases, the latter is actually experiencing a more harsh oxidizing condition, which can be explained in two aspects: (i) A high temperature is conducive to improving the hydrogen production efficiency; therefore, the SOECs' operating temperature is [75] for the in-flight particles in APS process; phase content (c) [75] in the coating as-sprayed or annealed at 700 • C for 2 h; temperature-dependent electrical conductivity of A-E coatings (d) [75] up to 800 • C; Inset: bulk material and as-sprayed coatings (d); cross-sectional SEM (e) [75] and EDX (f) [75] results of sample B; SEM (g) [75] and EDX (h) [75] results of sample E after 600 h oxidation at 800 • C; growth of oxide scales of the as-sprayed coatings under different spray parameters of (b) at 800 • C in 20 h (h) and 600 h (i) [75]; schematic diagram of the crack-healing process in air: as-sprayed coating (j); phase transformation from MeO rock salt structure to spinel structure (k); coating after the cracks are closed (l) [82].…”

“…As mentioned in Section 2.2, high-temperature oxidation of the FSS BPs mainly occurs on the SOFC-cathode and SOEC-anode sides [86]. Although both cases are exposed to oxygen-containing gases, the latter is actually experiencing a more harsh oxidizing condition, which can be explained in two aspects: (i) A high temperature is conducive to improving the hydrogen production efficiency; therefore, the SOECs' operating temperature is usually higher than that of SOFCs, bringing more stringent technical demands on the coating stability throughout its lifespan [45].…”