Corrosion behaviour of high aluminium steels in molten carbonate in an anode gas environment

Abstract

The corrosion behaviour of five ferritic steels with high aluminium content was investigated in (Li 0.60/Na 0.40)CO 3 melt in three different anode gas environments. The corrosion potentials were measured versus time, and the electrochemical techniques used for determination of the corrosion rates were linear polarisation resistance and Tafel extrapolation. The corrosion layer formed on the surface after electrochemical tests have been analysed by scanning electron microscopy (SEM) and glow discharge optical emission spectroscopy (GDOES). The evaluation of corrosion rates and corrosion resistance from the experimental electrochemical data by the conventional Tafel extrapolation and linear polarisation equations are not valid under these conditions. Therefore, a modified theoretical model has been used to evaluate the corrosion resistance and corrosion rates. In general, the corrosion resistance of high aluminium steels in molten carbonate melt, at anode gas environment, is much higher than that of 310 and 316 stainless steels. It has been shown that lower temperatures in combination with higher concentrations of carbon dioxide result in a higher corrosion rate.