Perovskite Conversion Coatings as Novel and Simple Approach for Improving Functional Performance of Ferritic Stainless Steel SOFC Interconnects

A novel type of iron conversion process has been recently developed to produce dense and adherent LaFeO3 perovskite coatings onto ferritic stainless steel surfaces by reaction with La2O3 dissolved in specially-formulated alkali molten carbonate baths. The major application of LaFeO3 perovskite coatings is for use as electrically conductive and Cr barrier layers for enhancing the functional performance of solid oxide fuel cell (SOFC) stainless steel interconnects. An overview of the molten salt bath conversion process including the effect of chemical accelerants on structure and morphology of the deposited perovskite coatings is illustrated in this work. Latest results on SOFC coating functional properties obtained in recent European Union (EU) funded projects are also briefly mentioned. In particular, the tight correlation between coating thickness and electrical functional properties in terms of area specific resistance is highlighted here. Although thickness dependency may indicate a mediocre electrical conductivity of LaFeO3 coatings produced by the conversion process, nonetheless very promising ASR results could be obtained in SOFC cathode environments at 700 degrees C with optimized coating structures and appropriate low coating thickness, thus suggesting a high potential of the conversion process for SOFC interconnect applications.