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Rhenium the Rarest of Rare Strategic Metals
This element has an atomic number of 75 and a symbol of Re on the periodic table of the elements. Rhenium is found in the earth’s crust at a concentration of approximately 1 ppm (parts per billion). The name rhenium comes from the Latin Rhenus meaning Rhine. This rare strategic metal was discovered in Germany in 1925 by Walter Noddack, Otto Berg and Ida Tacke hence the name Rhenium named after the river Rhine. The metal was the last stable element to be discovered. It is considered a transition metal.
Rhenium is so rare that is not directly mined. It is a by-product of copper and molybdenum mining. To put it in perspective the team at GE (General Electric), put this together.
“It takes, on Average, approximately 120 metric tons (264,554 pounds) or the equivalent weight of 44 Cadillac Escalade SUV´s- of copper ore to produce 1 ounce of rhenium- or the equivalent of five U.S. quarter coins.”
Total world production of Rhenium is between 40 and 50 metric tons per year. The top producers are Chile, United States, Kazakhstan and Peru. Recycling Rhenium also provides approximately 10 metric tons to the annual supply.
Rhenium is so important to industry because it has the third highest melting point of all elements. Tungsten and Carbon are the only elements with higher melting points. Rhenium has a few uses but 70% of all that is used per year, is used in the aviation industry. Rhenium is used in High temperature superalloys. The largest users of Rhenium in industry are Rolls Royce, General Electric and Pratt & Whitney. These companies use up to 6% rhenium content in the nickel-based superalloys in their jet engines. The strategic metal is used in such aircraft engines as the F-15, F-16, F-22 and the F-35. This metal is critical to national defense.
Uses of Rhenium
- Superalloys in combination with nickel, tungsten and molybdenum
- Thermocouples in combination with tungsten for measuring temperatures up to 2200°C
- Filaments for mass spectrographs and ion gauges
- Photoflash lamps for photography
- Treating liver cancer
The continuing rise in demand of the strategic metal has put pressure on the supply side. Over the last few years the price of Rhenium has been rising steadily. This has forced companies like General Electric to find more creative ways to recycle the element. Investors have also been buying the metal and storing it through companies like Swiss Metal Assets in their Defense basket of metals. It will be interesting to see what the future holds for rhenium and the other rare strategic metals.