Oxidation and electrical behavior of nickel/lanthanum chromite-coated stainless steel interconnects

Solving the contact resistance and cathode-chromium-poisoning problems associated with the application of ferritic stainless steel as solid oxide fuel cell interconnects is the objective of numerous current research efforts. In this work, the application of electrodeposited Ni/LaCrO3 composites for AISI 430 stainless steel as protective/conductive coatings has been studied, with emphasis on the oxidation behavior, scale structure and electronic conductivity of these coatings. The oxidation tests were performed at 800 °C in air for up to 2040 h. The results showed that the scale is a double layer consisting of a particle filled chromia-rich subscale and an outer Ni/Fe-rich spinel together with NiO. The addition of LaCrO3 particles greatly enhances the high-temperature oxidation resistance of Ni-coated ferritic stainless steel. Cavities, which form beneath the scale for uncoated steels as a result of cation outward diffusion, reduce the actual contact area between the scale and the alloy resulting in a high area specific resistance (ASR) as well as scale spallation. Excellent, stable ASR (0.005 Ω cm2 after 400 h) was achieved with the application of Ni/LaCrO3 coatings.