CORROSION OF TYPE 625 ALLOYS IN CHLOROALUMINATE MELTS

Corrosion properties of type 625 alloys (Inconel 625 and Nicrofer 6020) in 3 KCl -AlCl melts were investigated in a wide range of temperatures and various exposure time intervals using gravimetric tests and energy-dispersive X-ray spectroscopy of corroded samples surface. It was shown that corrosion processes have electrochemical nature and the increase of temperature up to 650 °С leads to change of corrosion mechanism from gradual etching towards intergranular corrosion. It was demonstrated that intergranular destruction is associated with formation of secondary phases at the grain boundaries of alloys. “Time-temperature-precipitation” diagram was constructed to predict the possible conditions of type 625 alloys application. It was found that Inconel 625 and Nicrofer 6020 alloys can be used in contact with chloaluminate melts at temperatures less than 600 °С