Corrosion behavior of Fe-Cr alloys in Li2CO3-K2CO3 molten carbonate

The corrosion in binary alloys, Fe-16 wt % Cr, Fe-20 wt % Cr, and Fe-25 wt % Cr, by 42.7/57.3, 50.0/50.0, and 62.0/38.0 mol % Li2CO3/K2CO3 melts was investigated by immersion tests and AC impedance measurements. Electron microscopy, X-ray diffraction, X-ray microanalysis, and chemical analysis were applied to characterize the structure and chemical composition of the corrosion products. The corrosion products contain an outer LiFeO2, an inner LiCrO2, and a middle mixed LiFeO2-LiCrO2 layer. The thickness of the outer and midlayer decreases with increasing Cr content. The overall result shows that the 50/50 melt causes the least corrosion to the alloys, and for each melt the alloys of larger Cr contents have higher corrosion resistance. The AC impedance data were analyzed by a corrosion model in terms of a parameterized equivalent circuit. (c) 2005 The Electrochemical Society.