Rhenium: an Exotic Metal in Chemistry and for Alloys

From the beginning of the bronze age, i.e. for around 7,500 years, metals have been an integral part of man's everyday life. Since that time, more and more sophisticated alloys have been developed and continuously improved: Iron succeeded bronze, and with the discovery of suitable additives, iron was turned into steel. For use under extreme conditions – for instance in aircraft engines or power station turbines – metallurgists dug even deeper into their bag of tricks and produced "Super-alloys": nickel or cobalt-based high-performance alloys containing rhenium.

Super-alloys excel through high mechanical strength as well as high resistance to corrosion, and temperature stability. These properties are due, in part, to the use of the metal rhenium in the alloys. W.C. Heraeus has already been processing rhenium on an industrial scale for around 20 years.

The corrosion resistance of super-alloys is affected to a considerable extent by contaminations: A maximum of 10 foreign atoms per 1,000,000 rhenium atoms is permitted. This ratio illustrates that for processing rhenium a reliable quality management presupposes sophisticated, high-performance analysis systems.

However, also processing itself presented a challenge to W. C. Heraeus' engineers and technicians. For few years now, our Chemical Products business unit has been using a new method for the production of rhenium. During this process it is obtained in the form of a high-purity powder, which is then turned into solid pellets measuring appr. 10 millimeters in diameter by pressing and sintering. These pellets allow alloys to be doped more accurately than with the rhenium powders used previously. In addition, the pellets have a smaller surface area, a fact which drastically reduces the danger of contamination.

Developing this new process, Heraeus technicians made an important step forward: W. C. Heraeus is now able to process alloying or melting residues or grinding and cutting swarf with a low rhenium concentration. This development has enabled Heraeus to gain a technological lead. Without our longstanding experience of special and precious metals, this certainly would not have been possible.

For many years W. C. Heraeus GmbH & Co. KG has been an established supplier of Re compounds (e.g. ammonium tetraoxorhenate(VII); "Ammonium Perrhenate") and their solutions (e.g. hydroxotrioxorhenium(VII) solution; "Perrhenic Acid") to (petro)chemistry. Moreover, we are able to recover the metal from spent catalysts.