The Bureau of Mines conducted corrosion tests of 18 commercial alloys in h3po4-phosphate rock or al2o3 slurry, in 10 pct hf, and in 25 pct h2sif6 to simulate three environments anticipated in a Bureau process to extract fluoride values from phosphate rock. Small alloy coupons were rotated in duplicate tests at 4.4 to 21 fps in the slurry at 170 deg c to determine rates of erosion-corrosion. At 4.4 Fps the lowest rates, in mils penetration per year (mpy), were measured for hastelloy c-276 (<20), hastelloy b (30), and inconel 625 (150); the rates increased at 21 fps to 55 mpy, 45 mpy, and 1,000 mpy, respectively. The corrosion rate for all alloys exceeded 40 mpy in either the equilibrium vapor or liquid phases of aqueous solutions containing 10 pct hf or 25 pct h2sif6 at 100 deg c. Uniform corrosion in 10 pct hf at 50 deg c was observed only for inconel 625 (22 mpy), hastelloy c-276 (43 mpy), and illium 98 (17 mpy). Inconel 625 (0.75 Mpy), hastelloy c-276 (1.3 Mpy), illium 98 (1.7 Mpy), and incoloy 825 (0.45 Mpy) were attacked uniformly in 25 pct h2sif6 at 50 deg c.