From Wedding Bands to Catalytic Converters

The platinum-group metals comprise six distinct types: iridium, palladium, platinum, osmium, rhodium and ruthenium. The catalytic properties of these metals is excellent. For example, platinum’s wear and tarnish-resistance characteristics are well-suited for making fine jewelry. Other distinctive properties are resistance to chemical attack, excellent high-temperature characteristics and stable electrical properties.

Since 1979, the automotive industry has emerged as the principal consumer of platinum-group metals. Palladium, platinum and rhodium have been used as oxidation catalysts in catalytic converters to treat automobile exhaust emissions by reducing the toxicity of emissions from an internal combustion engine. In addition to their use on automobiles, catalytic converters are also used on forklifts, mining equipment, trucks, buses, trains and other engine-equipped machines. A catalytic converter provides an environment for a chemical reaction whereby toxic combustion byproducts are transformed into less-toxic gases.

Platinum-supported catalysts are used in the refining of crude oil, reforming and other processes used in the production of high-octane gasoline and aromatic compounds for the petrochemical industry.

Other uses for platinum-group metals include:

Iridium: As a material, iridium is difficult to work with because of its high hardness, high melting point, and high stiffness and brittleness. Its main uses are as an alloying element in platinum to increase its hardness or as an alloy with osmium to make into such items as compass bearings. It is also used in electrical equipment and contacts, as well as on sparkplug points of some vehicles to improve the ignition of the fuel, which improves performance and reduces emissions. Radioactive iridium-192 is used for the treatment of prostate cancer.

Palladium: An extremely pliable material, palladium can be rolled into thin sheets or drawn into fine wire. It is very resistant to corrosion, but susceptible to attack from strong acids. Palladium is used to purify gas in catalytic converters, as an alloying element in white gold for jewelry, in scientific instruments and for electroplating. Palladium is also used in dentistry as filling material and sometimes in dental instruments.

Platinum: Platinum is soft and malleable, with good resistance to corrosion and chemical contact. It is used in a number of different applications, including electrical resistance wires, electrodes, catalytic converters, coatings on missile nose cones, jet engine fuel nozzles, jewelry, electrical contacts and photography. Platinum is the only metal that can be successfully soldered to glass without causing it to break.

Osmium: This is the heaviest known element, with a density nearly three times that of steel. Like iridium, osmium is difficult to work with because of its high hardness property and brittleness. Osmium is impervious to attack from water and air and is not attacked by acids. However, some molten alkalis can react with it.

Rhodium: Because of its limited availability, rhodium is the world’s most expensive metal. It is primarily used as an alloying element to increase the hardness of platinum and palladium. Rhodium is used for electroplating platinum jewelry, to increase the hardness of the material in order to reduce the amount of wear, and to provide a brighter, more attractive surface.

Ruthenium: This mineral resists chemicals well and is used in the electrochemical industry to coat titanium electrodes for use in the manufacturing processes of chlorine. Ruthenium is also used as a catalyst to convert chemical energy into electrical energy; and these catalysts are used to extract hydrogen from natural gas.

References:
USGS Minerals Information: Platinum-Group Metals/Statistics and Information
The DTI Manufacturing Advisory Service – fact shee