The Solid Oxide Cell (SOC) stacks are complicated multi-layered systems consisting of SOCs, sealing, and metallic components such as separators and interconnects. The interconnects are usually made of ferritic steel containing a high chromium content (above 20%) and with special alloying additives dedicated to SOC applications. However, using even these highly specialized types of steel causes some challenges. The high corrosion resistance of ferritic steel stems from the formation of a Cr2O3 scale and the decrease of the Cr concentration in the alloy as this scale grows with time. In the case of thin components or during the long-time operation of the stack the Cr content may decrease beneath the critical level where breakaway oxidation occurs, significantly limiting the durability of the interconnect. Another problem is the volatilization of Cr (VI) species that occurs at the operating temperature of the system (600-800 °C). Formed volatile chromium compounds migrate into the air electrode, and consequently lead to the reduction of its catalytic activity. Therefore, the surface of the interconnect is covered with a ceramic protective coating, which minimizes or eliminates the harmful effects of chromium compounds on the stack performance. Most of the literature reports concern the use of manganese-cobalt oxides with a spinel structure for this purpose. Those oxides possess good electrical conductivity and their thermal expansion coefficient (TEC) matches TEC values of the other stack components. However, the toxicity of cobalt, its limited resource, and supply uncertainties make it difficult to implement SOC technology on an industrial scale - forcing the use of alternative materials devoid of cobalt as protective layers. Nevertheless, the mere application of ceramic coatings on interconnects may be insufficient, especially in the context of steel corrosion, therefore in this work, the modification of the steel preparation is proposed as a complementary action to extend interconnects durability.
Hence, the conducted research was concerned with verifying the effect of additional thermal treatment of the steel substrate depending on the used temperature and atmosphere. The pre-oxidized steel samples were coated with protective layers differing in the ceramic powder. For studies, Mn1.5Co1.5O4 (MC11) oxide - a commonly used spinel oxide in the function of protective layers, and alternative cobalt-free based on copper materials: CuMn2O4 (CM2), CuMn1.9Fe0.1O4 (CMF) were used. Protective layers were applied using the electrophoretic deposition (EPD) method. The area specific resistance (ASR) of the prepared samples was measured in air and the microstructure of the coatings, as well as contact between coatings and steel, were evaluated by the SEM technique.  
 
Authors would like to acknowledge financial support from Ministry of Science and Higher Education through the statutory grant (grant number CPE.4000.001.2023).