Fabrication of Co3O4 and La0.6Sr0.4CoO3−δ-Ce0.8Gd0.2O2−δ dual layer coatings on SUS430 steel by in-situ phase formation for solid oxide fuel cell interconnects

Dual layer coatings Co3O4 and La0.6Sr0.4CoO3−δ-Ce0.8Gd0.2O2−δ are developed for solid oxide fuel cell (SOFC) metallic interconnects by a combined approach. The cobalt for protective layer is deposited by electroplating, and the composite La0.6Sr0.4CoO3−δ precursors-Ce0.8Gd0.2O2−δ for cathode contact layer is applied by screen printing. The dual layer coatings are sintered at 1100 °C in Ar atmosphere, in order to not only achieve good bonding and adhesion, but also reduce oxidation damage to SUS430 ferritic stainless steel substrate. The phases of Co3O4 and La0.6Sr0.4CoO3−δ are in-situ formed by subsequent oxidation at 800 °C in air. The chemical composition, structure and morphology of the dual layer coatings are analyzed by XRD, SEM and EDS. Area-specific resistance (ASR) of the coated substrates has also been tested in a simulated operating condition of SOFCs for up to 200 h. It is found that the dual layer coatings effectively block chromium diffusion and improve the oxidation resistance of the metallic substrate. The interconnect with dual layer coatings exhibits a reduced ASR of 22.8 mΩ cm2 as compared to uncoated one with ASR of 64 mΩ cm2 after isothermal oxidation at 800 °C for 200 h.