Preparation and performances of CuCo spinel coating on ferritic stainless steel for solid oxide fuel cell interconnect

A compact and adherent CoCu spinel coating on ferritic stainless steel was developed by electroplating a CoCu alloy layer followed by oxidation. The CoCu alloy was oxidized into a three-layer structure consisted of a thinner CuO outer layer, a middle thicker Cu0.92Co2.08O4 layer and an inner Co3O4 layer after an oxidation treatment of 2 h at 800 °C in air. The three-layer oxide structure was transformed into a double-layer scale with a (Co,Cr,Cu,Mn,Fe)3O4 spinel outer layer and an inner Cr-rich oxide layer after an oxidation of 500 h at 800 °C in air. The CuCo coating enhanced the oxidation resistance of the alloy and served as a diffusion barrier against the outward migration of Cr elements. Meanwhile, the area specific resistance (ASR) of the scale for the CuCo coated alloy was significantly lower than that for the bare sample.