Ultrasonic Sprayed for Solid Oxide Fuel Cells
CuFe2O4/CuO bilayer protective coating deposited onto SUS430 interconnects by ultrasonic sprayed for solid oxide fuel cells
Solid oxide fuel cells (SOFCs) are high-efficiency energy conversion devices that directly convert the chemical energy of fuel into electrical energy. Since individual cells produce low output voltages, they must be stacked in series using metallic interconnects to increase power output. SUS430 ferritic stainless steel is a commonly used interconnect material due to its excellent compatibility; however, under high-temperature oxidizing conditions, a chromium oxide layer forms on the steel surface. This layer tends to volatilize into chromium species that deposit at the cathode interface, causing issues such as cathode poisoning and the degradation of electrode activity. Furthermore, the continuous thickening of the oxide layer increases the area-specific resistance, while thermal expansion coefficient mismatch during thermal cycling can lead to coating spallation, severely limiting the service life of the cell stack. Consequently, the development of high-performance protective coatings is of significant engineering value.
Spinel coatings have emerged as mainstream protective materials due to their high electrical conductivity and strong adhesion. Among them, CuFe₂O₄ is an excellent candidate for protective coatings, offering low cost, a compatible thermal expansion coefficient, and superior electrical conductivity, while effectively blocking oxygen ingress and chromium outward diffusion. Research indicates that a CuO layer provides a more effective barrier against chromium and manganese diffusion than a single CuFe₂O₄ coating. Additionally, the extremely low solid solubility of iron in CuO facilitates the formation of a composite dual-phase structure that balances protective performance with electrical conductivity, providing a theoretical basis for dual-layer coating designs.
In this study, ultrasonic spraying—a technique characterized by a simple process, high raw material utilization, and excellent coating uniformity—was employed to prepare a CuFe₂O₄/CuO dual-layer protective coating on SUS430 stainless steel. The inner layer consists of a highly conductive and adherent CuFe₂O₄ spinel, while the outer layer is a highly effective CuO barrier, thereby combining the performance advantages of both materials. Experimental results demonstrate that the dual-layer coating features uniform coverage, strong adhesion, and excellent high-temperature structural stability, effectively suppressing substrate oxidation and chromium diffusion. In a long-term oxidation test conducted at 800°C for 1,000 hours, the bilayer coating—compared to bare steel and a single-layer CuFe₂O₄ coating—limited the chromium oxide layer thickness to approximately 3 μm, significantly reduced the oxidation rate constant, and achieved a protection efficiency of 86.6%. Electrical performance tests demonstrated that the coated sample exhibited an area-specific resistance (ASR) of only 2.4 mΩ·cm² after 1,000 hours of aging, consistently maintaining low resistance. Electrochemical tests confirmed that the coating effectively mitigates the degradation of the oxygen reduction reaction caused by chromium poisoning, thereby stabilizing cathode activity and the interface structure.
In summary, the CuFe₂O₄/CuO bilayer coating combines the high electrical conductivity of spinel materials with the superior diffusion-blocking capability of CuO. The scalable preparation process effectively addresses the challenges of high-temperature oxidation and chromium volatilization in stainless steel SOFC interconnects, offering a reliable technical solution for the surface modification of high-performance, long-life SOFC interconnects.
About Cheersonic
Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.
Our coating solutions are environmentally-friendly, efficient and highly reliable, and enable dramatic reductions in overspray, savings in raw material, water and energy usage and provide improved process repeatability, transfer efficiency, high uniformity and reduced emissions.
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