Iridium is a rare precious metal, but it is expensive, not delicate. Iridium has a density of 22.65g/cm3, the highest of any known element. Iridium has a high melting point (2454℃), so iridium products can be used at high temperatures (the temperature range is 21-2200℃), but their low temperature plasticity is poor. Iridium is also the most corrosion-resistant metal, and ordinary corrosives cannot corrode iridium. The dense iridium is insoluble in all inorganic acids and is impervious to other metal melts, such as molten lead, zinc, nickel, iron, gold, etc. It resists many melting agents and high temperature silicates. Iridium alloys, like other platinum-group metal alloys, have strong adsorption capacity for organic compounds and can be used as catalyst materials.
Iridium has the advantages of high melting point, strong corrosion resistance and so on. It is widely used in aerospace, medicine, automobile and other industries.
Iridium has high melting point and high stability, but its brittleness and high temperature loss limit its application. Iridium was originally used as a pen tip.
Later, it was used for needle injection, balance sheet, compass holder, electric contact, etc. Experimental containers made of platinum-iridium alloy, such as crucible, electrode, resistance wire, etc., are necessary for chemical laboratories. Iridium crucibles can be used to grow refractory oxide crystals. Crucible can operate for thousands of hours at 2100 to 2200℃. The high temperature oxidation resistance and thermoelectric properties of iridium make the iridium/iridium thermocouple the only precious metal temperature measuring material that can measure the atmospheric temperature up to 2100℃. Iridium can be used as a container material for radioactive heat sources. Iridium oxide film is a promising electrochromic material. Ir192 is a gamma ray source that can be used for nondestructive testing and chemoradiotherapy.
