Platinum (Pt) belongs to both the refractory as well as the noble metals. Noble metals are highly resistant to chemical attack, even at high temperatures. While refractory metals are extremely heat resistant and highly durable. These factors, combined with excellent thermo-electric properties, makes platinum an ideal sheath material for temperature control in highly demanding environments.
With the addition of rhodium (Rh) as a 10% or 20% alloy, all these favorable characteristics of platinum are preserved while improving the mechanical strength at higher operating temperatures.
Furthermore, in comparison to ceramic sheaths, platinum and its alloys are much more flexible which is a very useful characteristic when placing thermocouples in intricate spaces.
Physical properties
Platinum 10% rhodium
| Composition | PT 90%, Rh 10% |
| Melting point | 1840°C to 1870°C |
| Maximum operating temperature | 1700°C |
Platinum 20% rhodium
| Composition | PT 80%, Rh 20% |
| Melting point | 1900°C |
| Maximum operating temperature | 1800°C |
Other physical properties include:
- Ductility (flexibility) with a bend radius of up to five times the diameter without loss of mechanical strength
- Due to the resistive properties of platinum the overall diameter is smaller than when using other sheath materials. This can be an advantage in certain applications with limited space.
- Resistance to thermal shock which means the platinum alloy sheath can withstand rapid fluctuations in temperature without damage.
Industrial applications of platinum
Platinum alloy sheaths are suited to oxidizing and inert environments or any intensely corrosive conditions. Some of the industries where they are used include:
- Steel (annealing furnaces)
- Glass (the sheaths can withstand direct contact with molten glass)
- Nuclear (long exposure to very high temperatures)
- Automotive (catalysts)
Kamet’s platinum products
| Min OD (mm) | Max OD (mm) | TC type possible (type) | |
|---|---|---|---|
| Pt10%Rh | 1.00 | 4.78 | K, J, B, R, S |
| Pt20%Rh | 1.00 | 4.78 | K, J, B, R, S |
Kamet supplies Pt10%Rh and Pt20%Rh thermocouple sheaths of excellent quality.
As experts in sheath materials we are able to assist you with any questions you might have. Thanks to our large network of global manufacturers we offer a wide range of MI cable and thermocouples with special sheath materials. A range of customization options is available for any unique challenges, so please feel free to contact us.