Metallic impurities induced corrosion of a Ni-26W-6Cr alloy in molten fluoride salts at 850 oC

Highlights: • Ni-26W-6Cr alloy shows a good corrosion resistance to FLiNaK salts at 850 °C. • Cr depletion from the alloy is accelerated by its reaction with Fe impurities. • The depletion of W is mainly caused by the presence of Mo impurities. • The depletion of W can influence the neutron spectra of reactors. The effect of metallic impurities on corrosion of a Ni-26W-6Cr alloy in molten FLiNaK salts at 850 °C was investigated. Results show that the Ni-26W-6Cr alloy exhibits the same excellent compatibility with fluoride salts as Hastelloy N alloy. Fe impurities in molten salts accelerate the diffusion of Cr in the alloy, which determines the corrosion degree of the alloy. Unexpected depletion of W from the alloy was observed, which mostly results from the presence of Mo impurity in the salts. Mo impurity should be limited because of the significant effect of W on the neutron spectra of reactors.