Effect of Fe on the oxidation behavior, electrical properties and microstructure of CoNi protective coatings for metal interconnect layers in solid oxide fuel cells

CoNi and 5% Fe doping CoNi alloy coatings are prepared on SUS 430 substrates as interconnect protect layers for solid oxide fuel cells by electroplating. The electrical characteristics and oxidation resistance of interconnects are enhanced by the alloy coatings after they are oxidized in air at 800 °C for 1000 h and the Co-Ni-Fe alloy coatings showing the better effect. Cr is unable to diffuse outward owing to the multi-layer oxidation structure. Addition of Fe to CoNi alloy coatings leads to the formation of a (Fe,Co,Ni)3O4 spinel layer with lower activation energy and stronger ability to restrict oxygen diffusion inward.