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Platinum Group Metals (PGMs)

What are PGMs?

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Platinum Group Metals (PGMs)

Platinum bars and shot.

Image © Johnson Matthey

The platinum group metals (PGMs) are six transitional metal elements that are chemically, physically and anatomically similar. PGMs include

Characteristics:

The PGMs are the densest known metal elements. Exceptionally rare, the six metals naturally occur in the same ore bodies. They are highly durable and, due to their high value, often recycled, giving them long life cycles.

Platinum and palladium are soft and ductile. They resist oxidation and high temperature corrosion and are often used as catalysts. Catalysts speed up chemical reactions without themselves being chemically altered in the process.

Rhodium and iridium are harder and more difficult to work with, however, chemical compounds of these two metals are valued in a number of alloy applications. Rhodium is valued as a catalyst material.

Ruthenium and osmium are hard, brittle and have poor resistance to oxidation, but are valuable alloy additives and catalysts.

Applications:

PGMs are most often used as catalysts because of their chemical stability, but they are not limited to this role. According to the International Platinum Group Metals Association (IPA), one quarter of all goods manufactured either contain a PGM or had a PGM play a key role in its production.

Some examples of end-use applications include: in catalysts for the petroleum industry (palladium and platinum), in pacemakers and other medical implants (iridium and platinum), as a stain for fingerprints and DNA (osmium), in the production of nitric acid (rhodium), and in chemicals, such as cleaning liquids, adhesives and paints (ruthenium).

Properties:

Platinum Palladium Rhodium Iridium Ruthenium Osmium
Chemical Symbol Pt Pd Rh Ir Ru Os
Density (g/cm3) 21.45 12.02 12.41 22.65 12.45 22.61
Melting point (°C) 1,769 1,554 1,960 2,443 2,310 3,050
Vickers hardness no.* 40 40 101 220 240 350
Electrical resistivity
(microhm.cm at 0°C)
9.85 9.93 4.33 4.71 6.80 8.12
Thermal conductivity
(watts/metre/°C
73 76 150 148 105 87
Tensile strength*
(kg/mm2)
14 17 71 112 165 -

Source: Johnson Matthey. www.platinum.matthey.com

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