Pre-treatment and oxidation behavior of sol–gel Co coating on 430 steel in 750 °C air with thermal cycling

Research and development efforts continue to improve oxidation resistance and electrical conductivity of solid oxide fuel cell (SOFC) interconnects. This research evaluates the performance of a ferritic stainless steel (AISI 430 — a candidate SOFC interconnect material) with and without a Co coating (via sol–gel dip coating technique) with various pre-treatments, during cyclic oxidation exposures up to 750 °C in laboratory air. A pre-treatment exposure of Co coated samples to a 750 °C reducing atmosphere (prior to oxidation exposures) led to the formation of an effective Co-based spinel oxide coating that lowers oxidation rates by more than 40 times, and substantially lowers area specific resistance (ASR) in comparison to uncoated specimens. The development of effective sol–gel Co coatings with reducing pre-treatments, and their evolution within simulated SOFC interconnect environments is presented and discussed.

► Cobalt has significant effect on increasing the conductivity of protective coating.
► It seems there is a conflict in literatures as application of cobalt containing coatings.
► We attempted to clarify the oxidation mechanism and made promising cobalt coating.
► Coating was applied via sol–gel technique with use of reducing atmosphere pre-treatment.
► Oxidation kinetics and electrical conductivity testing approved the applicability of this approach.