Electrodeposition of yttria/cobalt oxide and yttria/gold coatings onto ferritic stainless steel for SOFC interconnects

Durability seems to be the single most critical issue for the widespread application of SOFCs. Among critical issues, the stability of interconnects – operating at high temperatures in aggressive gas environments – calls for the selection of cheap materials exhibiting high corrosion performance, accompanied by low surface contact resistance. Use of coated AISI 430 stainless steel is currently the state-of-the-art choice. In this paper we propose Y2O3, Y2O3/Co3O4 and Y2O3/Au composite films as innovative coatings for AISI 430 plates. These coatings were electrodeposited from chloride salts dissolved in hydroalcoholic solutions containing chitosan as binder. The evolution of the crystalline structure of the electrodeposits with heat-treatment conditions has been studied by XRD, their chemical composition has been evaluated by EDX analysis, their morphology has been observed by SEM and the adhesion has been measured by scratch testing. Coated samples were oxidised in air at 800 °C for times up to 500 h and the area-specific resistance (ASR) as a function of exposure time has been measured. All the coated samples developed ASR values below 100 mΩ cm2, the target value for SOFC applications. The ASR was found to increase in the order: Y2O3/Au, Y2O3, and Y2O3/Co3O4.