High-Temperature Corrosion of Metals in the Salt and Metallic Melts Containing Rare Earths

A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl-KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750-1050 degrees C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m(2) h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m(2) h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m(2) h) corresponding to the 8-th grade of stability and placing tantalum to the group of low stability materials.