Suppression of Cr evaporation by Co electroplating and underlying Cr retention mechanisms for the 22 wt.% Cr containing ferritic stainless steel

High temperature oxidation behavior and associated Cr evaporation process of Co electrodeposited 22 wt.% Cr containing ferritic stainless steel designed for the SOFC interconnects was investigated using XRD and post-processed TEM compositional analysis. The electrodeposited Co layer with a thickness of 400 nm lead to a tenfold reduction in the Cr evaporation. This results from not only the prevention of direct exposure of Cr2O3 to the air by Co spinel oxide formation but also the suspension of Cr transport through oxide grain boundaries due to the phase transformation of Co oxide from Co3O4 to MnxCo3-xO4.