Investigation of the Corrosion Resistance of Nickel-Molybdenum Alloys in the Eutectic LiF–NaF–KF

The corrosion characteristics of the nickel-molybdenum alloys Hastelloy-N mod. (USA), GH3535 (China), KhN80MTYu (Russia), and KhN80MTB (Russia) were studied in the melt 0.465LiF–0.115NaF–0.42KF at temperature 750°C with added metallic tellurium, a fission simulator, and ytterbium to lower the redox potential. The corrosion rate of the alloys is in the range 100 ± 15 μm/yr and is due to the high rate of the oxidation reaction on free fluorine ions of the most active metals on the surface of the alloys: dopants, chromium, and to a lesser degree molybdenum. The data obtained in the present work permit the conclusion that the mechanism of selective corrosion of the studied alloys is diffusion-controlled. The highest resistance at 750°C obtains in the alloy KhN80MTB. The alloys Hastelloy-N and GH3535 exhibit high telluric intercrystalline corrosion.