Degradation behaviour of Al–Fe coatings in wet-seal area of molten carbonate fuel cells

The corrosion resistance of Al–Fe coatings increases as a protective LiAlO2 layer forms. If, however, the Al–Fe coatings lack sufficient aluminium for maintaining this protective layer, the corrosion resistance of the coating is degraded by the growth of non-protective scales, such as LiFeO2. In this study, the degradation behaviour of Al–Fe coatings is investigated in the wet-seal environment of molten carbonate fuel cells (MCFC). Al–Fe coated specimens with various amounts of aluminium in the range 8–70 at.% and bulk specimens of Fe–23.9 Al (at.%) are prepared. A corrosion test is performed in Li/K carbonate systems at 650 °C with a single-cell and an immersion test. Test results reveal that aluminium contents in the coatings should be higher than 25 at.% in order to form and maintain a protective LiAlO2 layer. In addition to aluminium content, the influence of microstructural features on the degradation behaviour of Al–Fe coatings is discussed.