Preparation and performances of Co–Mn spinel coating on a ferritic stainless steel interconnect material for solid oxide fuel cell application

Ferritic stainless steels have become the candidate materials for interconnects of intermediate temperature solid oxide fuel cell (SOFC). The present issues to be solved urgently for the application of ferritic stainless steel interconnects are their rapid increase in contact resistance and Cr poisoning. In the present study, a chloride electrolyte suspension has been developed to electro-deposit a Co–Mn alloy on a type 430 stainless steel, followed by heat treatment at 750 °C in argon and at 800 °C in air to obtain Co–Mn spinel coatings. The experimental results indicate that an adhesive and compact Co–Mn alloy layer can be deposited in the chloride solution. After heat treatment, a complex coating composed of an external MnCo2O4 layer and an inner Cr-rich oxide layer has been formed on 430SS. The coating improves the oxidation resistance of the steel at 800 °C in air, especially in wet air, and inhibits the outward diffusion of Cr from the Cr-rich scale. Moreover, a low contact resistance has been achieved with the application of the spinel coatings. •Co–Mn alloys are deposited in chloride solutions to protect metallic interconnects.•The Co–Mn alloy is converted into adhesive spinel coatings by heat treatment in air.•Spinel coatings consist of an external MnCo2O4 layer and an inner Cr-rich layer.•spinel coatings inhibit the oxidation of the steel at 800 °C in air and air-10%H2O.•Spinel coatings decrease the area specific electrical resistance of the steel.