Cu-Fe Spinel Coating as Oxidation Barrier for Fe-16Cr Metallic Interconnect in Solid Oxide Fuel Cells

A conductive spinel CuFe2O4 is used to protect the metallic interconnect of solid oxide fuel cells (SOFCs) from oxidation and prevent the cathode from chromium poisoning. It is coated by the sol-gel method on a typical metallic interconnect material of Fe-16Cr alloy and evaluated by oxidation at 800°C for 200 h in air (the cathode atmosphere) under an applied current of 0.5 A cm−2. The results show that the coating is promising in providing oxidation resistance, and the oxide scale formed on both the positive and negative sides of the substrate are similar, which consists of a thin inner layer of Cr2O3, a middle layer of Cu-doped MnCr2O4 and a top layer of Fe2O3 with an overall thickness around 2 μm and grows less than 0.5 μm during the 200 h oxidation. The extrapolated area specific resistance (ASR) of the oxide scale at 800°C is approximately one seventh that formed on the uncoated Fe-16Cr alloy, suggesting that the outward migration of cations from the alloy substrate to the oxide scale is driven by the gradient of chemical potential rather than that of electrical potential in this particular situation due to the relatively high scale conductivity.