Molten salt synthesis of perovskite conversion coatings: A novel approach for corrosion protection of stainless steels in molten carbonate fuel cells

Abstract A novel conversion coating process has been developed to meet the stability requirements of stainless steel hardware in the demanding MCFC fuel cell environments. The process applies a perovskite-based coating by exploiting spontaneous oxidizing reactions of the metallic surface with La 2 O 3 in eutectic alkali carbonate mixtures. By using well controlled synthesis procedures, conversion coating layers covering the entire metallic surface with a uniform and compact structure could be obtained. The as-formed coatings with a surface morphology of agglomerated crystallite particles consisted of a thin ( 3 perovskite layer grown over a thicker (>5 μm) LiFeO 2 -rich layer. Test coupons of 316L stainless steel with the perovskite conversion coating were analyzed for corrosion protection and interfacial resistivity properties. It was found that the conversion coating is highly conductive while showing excellent long-term corrosion stability in simulated MCFC environments. These results suggested that perovskite coatings formed by molten salt conversion reactions could be particularly attractive to confer optimal protection and electrical continuity to MCFC current collectors.