Applying the Protective Mn–Co–La2O3 Coating on Crofer 22 APU Ferritic Stainless Steel Used as Solid Oxide Fuel Cell Interconnects

Abstract

This research studies the effect of Mn–Co–La₂O₃ coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plates in solid oxide fuel cells. The test samples were characterized by a field emission scanning electron microscope (FESEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The oxidation kinetics of the coated and uncoated samples were studied by tracking their weight changes over time at 800 °C, showing that the oxidation mechanism for all samples follows the parabolic law. Lower oxidation rate constant (k_p) values of the coated sample compared with that of the uncoated one indicated a reduction in the oxidation rate of the steel substrate in the presence of the Mn–Co–La₂O₃ coating. The examination of the cross-section of different samples after the isothermal oxidation for 500 h at 800 °C exhibited that applying the composite coating leads to a decrease in the thickness of the chromia layer formed on the steel surface. Furthermore, under these conditions, the area-specific resistance (ASR) of the coated sample (13.11 mΩ cm²) is significantly lower than that of the uncoated one (41.45 mΩ cm²).