Properties of PGM
Properties of platinum group metals
The six platinum group metals (pgm) are chemically very similar.
Platinum, iridium and osmium are the densest known metals, platinum
being 11 per cent denser than gold and about twice the weight of
the same volume of silver or lead. Palladium, rhodium and ruthenium
are lighter, palladium having about the same density as silver.
Platinum and Palladium are soft, ductile
and resistant to oxidation and high temperature corrosion. They
have widespread catalytic uses. In industry they are often used
with the addition of other metals, including other pgm.
Rhodium and Iridium are difficult to work,
but are valuable alone as well as in alloys. Their chemical
compounds have many uses, and rhodium is a particularly good
catalyst.
Ruthenium and Osmium are hard, brittle and
almost unworkable in the metallic state, with poor oxidation
resistance, but are valuable as additions to other metals, usually
other pgm, and as catalysts.
| |
Platinum |
Palladium |
Rhodium |
| Chemical Symbol |
Pt |
Pd |
Rh |
| Density (g/cm3) |
21.45 |
12.02 |
12.41 |
| Melting point (°C) |
1,769 |
1,554 |
1,960 |
| Vickers hardness no.* |
40 |
40 |
101 |
Electrical resistivity
(microhm.cm at 0°C) |
9.85 |
9.93 |
4.33 |
Thermal conductivity
(watts/metre/°C) |
73 |
76 |
150 |
Tensile strength*
(kg/mm2) |
14 |
17 |
71 |
| |
Iridium |
Ruthenium |
Osmium |
| Chemical Symbol |
Ir |
Ru |
Os |
| Density (g/cm3) |
22.65 |
12.45 |
22.61 |
| Melting point (°C) |
2,443 |
2,310 |
3,050 |
| Vickers hardness no.* |
220 |
240 |
350 |
Electrical resistivity
(microhm.cm at 0°C) |
4.71 |
6.80 |
8.12 |
Thermal conductivity
(watts/metre/°C) |
148 |
105 |
87 |
Tensile strength*
(kg/mm2) |
112 |
165 |
- |
* annealed condition