Effect of Fe on the oxidation behavior, electrical properties and microstructure of Co[sbnd]Ni protective coatings for metal interconnect layers in solid oxide fuel cells.

Co Ni and 5% Fe doping Co Ni 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 Co Ni alloy coatings leads to the formation of a (Fe,Co,Ni) 3 O 4 spinel layer with lower activation energy and stronger ability to restrict oxygen diffusion inward. • Two interconnect protective coatings were prepared by electroplating method. • The multilayer oxidized structure prevented the outward diffusion of Cr. • Co-Ni-Fe coated steels exhibited excellent oxidation resistance and lower ASR. • Co-Ni-Fe converted coatings were further characterized by TEM and EPMA. • (Fe,Co,Ni) 3 O 4 layer had excellent electrical properties and thermodynamic stability. [ABSTRACT FROM AUTHOR]