Influence of the Alloying Elements of the Stainless Steels on the Corrosion Behavior in Molten Carbonate

Abstract

Influence of the alloying elements and the crystal structure of the stainless steels on the corrosion behavior in molten carbonate was investigated by the immersion test at 650°C for 1000h. Weight loss and amount of dissolved alloying elements decreased with increasing the contents of Cr and Ni in stainless steel. Corrosion resistance of austenitic stainless steels was superior than of ferritic steels because Ni forming a solid solution with LiFeO₂ layer suppressed the outward diffusion of Fe with the formation of Cr₂O₃. In addition, it was revealed on the basis of the diffusion data that Cr₂O₃ formed on the austenitic steel has a tendency to inhibit the outward diffusion of Fe compared with that of the ferritic steels. Attempt made to use the austenitic stability index of stainless steel was pointed out the importance of the effect of the crystal structure for evaluating the corrosion behavior in the molten carbonate.