Oxidation and electrical behavior of ferritic stainless steel interconnect with Fe–Co–Ni coating by electroplating

Abstract

Fe–Co–Ni coating is deposited on ferritic stainless steel using a cost-effective technique of electroplating for intermediate-temperature solid oxide fuel cell (SOFC) interconnects application. The steel with Fe–Co–Ni coating has been evaluated in air at 800°C corresponding to the cathode environment of SOFC. The results indicate that the steel with Fe–Co–Ni coating experiences an initially large mass gain, and then the mass gain increases slightly after the first-week rapid oxidation stage. After thermal exposure in air at 800°C, the Fe–Co–Ni coating has been converted into (Fe,Co,Ni)3O4 spinel layer underneath which a Cr2O3 layer is developed from the steel substrate. The outer layer of (Fe,Co,Ni)3O4 spinel has not only suppressed Cr migration outward but also reduced the growth rate of the inner layer of Cr2O3. The steel with Fe–Co–Ni coating exhibits a stable surface oxide scale area specific resistance (ASR) which is much lower than that of the bare steel. (Fe,Co,Ni)3O4 spinel is a promising protective coating for SOFC steel interconnect.