Impedance spectra characteristics of Fe-Cr alloys in a solid K2SO4-KCl mixture at 600° and 650°

Abstract

The low temperature hot corrosion characteristics of Fe-10Cr and Fe-20Cr alloys is studied in solid 0.5K2SO4-0.5KCl mixture in air at 600° and 650°. A two-electrode system is arranged for electrochemical measurement, which has been proved effective in the study of solid- and molten-salt corrosion. EIS analysis discloses corrosion of Fe-Cr alloys goes through several different reaction stages during extended exposure, such as incubation, acceleration and catastrophic period. Additionally, all these stages are fitted by corresponding equivalent circuits and electrochemical elements, and simulation data of these models generally fits experimental data well. Different Cr content in Fe-based alloys has been investigated involving the active/oxidation process of metal Cr in solid 0.5K2SO4-0.5KCl mixture. Corrosion products in above-mentioned different stages are analyzed by scanning electron microscopy. The formation and depletion of protective scale in mixed salt is monitored. Corrosion rate and corrosion mechanism of Fe-10Cr and Fe-20Cr alloys are discussed, too.