Development of chromium barrier coatings for solid oxide fuel cells

The performance of electrolyte supported solid oxide fuel cell is impaired primarily due to poisoning of electrodes due to contaminants generated from the metallic components of the stack.Ferritic stainless steels are commonly used as stack material under severe operating conditions of SOFC environment. However, the high chromium content in this type of steels tends to form gaseous oxides and/or hydroxides which volatilize and condense on various components of stack assembly, particularly cathodes, resulting in performance degradation of the system.Two types of barrier coatings have been developed to minimize the chromium volatilization. In one case, coatings of oxide species were deposited by processes such as thermal and plasma spraying, and the other is by diffusion coating process such as aluminizing.This presentation will describe various barrier coatings, barrier properties provided by the coatings, and transpiration measurements adopted to evaluate the efficiency of those coatings.