Abstract <p>Protective coatings based on cobalt-manganese spinel for solid-oxide fuel cell (SOFC) interconnects made of stainless steel are synthesized by nonstationary electrolysis. According to X-ray diffraction data, the main phase of these coatings is Co₂MnO₄. The evolution of the microstructure of coatings is studied in operando in a SOFC cathode chamber. It is found that during the oxidation process, chromium and iron diffuse from the substrate into the coating, are oxidized, so that, after the service-life tests, the coating itself becomes a mixture of Co₂MnO₄, Fe₃O₄, and Cr₂O₃ oxides. Studying the dependence of the specific contact resistance of the interconnect/cathode junction on the time spent under a current load of 0.5 A cm^–2 in the model conditions of a SOFC cathode chamber in a measuring assembly for 1000 h at 850°C has shown that the resistance is about 35 mΩ cm^–2.</p>