Platinum-iridium alloy and iridium-rhodium alloy are both precious metal alloys for high-temperature and corrosive environments. They offer good corrosion resistance and thermal stability, but their composition, physical properties, processing characteristics, and typical applications are different.
Understanding these differences helps engineers and purchasing teams select the right alloy for specific operating conditions.
| Property | Platinum-Iridium Alloy | Iridium-Rhodium Alloy | |
|---|---|---|---|
| Main Composition | Platinum + Iridium | Iridium + Rhodium | |
| Common Grades | PtIr10, PtIr20, PtIr30 | IrRh10, IrRh40, IrRh60 | |
| Melting Point | Between Pt and Ir | Around 2450°C | |
| Corrosion Resistance | Excellent | Excellent | |
| Oxidation Resistance | Good | Better at very high temperatures | |
| Typical Applications | Electrical contacts, medical devices | Thermocouples, high-temperature components |
1. Chemical composition
Platinum-iridium alloy: It is a binary alloy based on platinum, mainly adding iridium elements. Common ones include PtIr10, PtIr17.5, PtIr25, PtIr30, etc.
Iridium-rhodium alloy: It is a binary alloy composed of iridium and rhodium. There are alloys such as IrRh10, IrRh40, IrRh50, and IrRh70.
2. Processing
Platinum-iridium alloy: The processing performance deteriorates with the increase of iridium content, and it must be processed by high-temperature hot processing before it can be cold-processed into materials.
Iridium-rhodium alloy: It is generally melted by argon protection in a high-frequency furnace, and the ingot is hot rolled and cold processed appropriately.
3. Physical properties
Density: The density of platinum-iridium alloy is generally between pure platinum (21.45 g/cm3) and pure iridium (22.56 g/cm3); the density of iridium-rhodium alloy is about 22 g/cm3.
Melting point: The melting point of platinum-iridium alloy is usually between the melting point of platinum, 1772℃, and the melting point of iridium, 2446℃; the melting point of iridium-rhodium alloy is as high as about 2450℃.
4. Chemical properties
Corrosion resistance: Among platinum-iridium alloys, alloys containing more than 30% iridium are not corroded by boiling aqua regia; iridium-rhodium alloy has excellent corrosion resistance and can stably exist in harsh environments such as high temperatures and strong acids.
Oxidation resistance: Platinum-iridium alloy has certain oxidation resistance at high temperature, but the high-temperature oxidation resistance of iridium-rhodium alloy is stronger than that of pure iridium. At 2000℃, IrRh60 loses about 5% of its weight by oxidation, while pure iridium loses as much as 27%.
5. Application field
Platinum-iridium alloy: It is a classic electrical contact material used for aircraft engine ignition contacts, high-sensitivity relays, and electrical contacts of micromotors, etc.; it can also be used to manufacture medical equipment such as pacemakers and dental implants, key components in aircraft engines or chemical pipelines, etc.
Iridium-rhodium alloy: Mainly used as high-temperature anti-oxidation thermocouples with an operating temperature of over 2000°C. It can also be used to manufacture high-reliability electrical contacts, electrodes, connectors, and other electronic components, as well as catalytic converters in petrochemicals or automobile exhaust systems, etc.
FANMETAL is a supplier of precious metal products with more than 20 years of professional experience. We can provide customers with wires, platinum materials, or electrode materials made of palladium-iridium alloy, platinum-iridium alloy, iridium-rhodium alloy, and platinum-rhodium alloy. These high-quality and cost-effective products have been exported to overseas countries such as the United States, Canada, Switzerland, Indonesia, Brazil, Hungary, Mexico, etc., and have received unanimous praise from customers. Although platinum-iridium alloy and iridium-rhodium alloy are both precious metals, they have subtle differences in characteristics and applications.
