Effect of Fe doped Co–Ni protective coatings on the oxidation behavior and electrical properties of SOFC alloy interconnect materials

In order to enhance the oxidation resistance and electrical properties of interconnects for solid oxide fuel cells (SOFCs), three Co–Ni alloy coatings with varying contents of Fe doping were prepared onto SUS 430 substrate using electroplating method and oxidized in air at 800 °C for 1000 h. The experimental results demonstrated that the alloy coating significantly enhanced both the oxidation resistance and electrical properties of the interconnect substrate. The multi-layer oxidation structure blocked Cr from diffusing outward. Notably, the (Co,Fe)3O4/(Ni,Co)O in the oxidized layer of 5% Fe doped Co–Ni coated steel completely transformed into (Fe,Co,Ni)3O4 spinel layer after long term oxidation, which had the lowest activation energy and the strongest ability of restricting oxygen diffusion inward. Thus, the 5% Fe doped Co–Ni coated steel showed superior oxidation resistance (kp = 8.76 × 10−14 g2 cm−4 s−1) and excellent electrical properties (ASR = 13.19 mΩ cm2) following oxidation for 1000 h.