Iridium-The world's most corrosion-resistant metal

Iridium-The world's most corrosion-resistant metal

Iridium metal reference price: 52887.98 USD/kg

Iridium is a chemical element, with the chemical symbol Ir. Iridium was discovered in insoluble impurities of platinum in 1803. The main discoverer, Smithson Tennant, named it Iridium, which originated from Iris due to its many different colored salts. Iridium is a rare element, with a production and consumption of three tons in the Earth's crust last year. Iridium 191 and iridium 193 are the only two natural isotopes and the only stable isotopes.

Iridium has stable chemical properties. Iridium is the most corrosion-resistant metal, with extremely high chemical stability to acids and insoluble in acids. Only sponge like iridium slowly dissolves in hot aqua regia. If iridium is in a dense state, even boiling aqua regia cannot corrode; However, in a sealed reactor under high temperature and pressure, iridium is significantly corroded in aqua regia at temperatures above 250 ° C; If a mixed acid composed of 20 parts of concentrated hydrochloric acid and 1 part of concentrated nitric acid is used, its corrosiveness to iridium is about 20 times that of aqua regia at the above temperature and pressure. Therefore, it is often used as a reagent for digesting metallic iridium in chemical analysis.

Iridium is one of the rarest elements in the Earth's crust, with an average mass ratio of only 0.001 parts per million. The abundance of gold is 40 times that of it, platinum is 10 times that of it, and silver and mercury are both 80 times that of it. It is worth mentioning that only three stable elements are rarer than iridium: rhenium, ruthenium, and rhodium, with the latter two having an abundance of one tenth that of iridium. In contrast, the content of iridium in meteorites is much higher, usually above 0.5 parts per million. Scientists believe that the content of iridium in the entire Earth is much higher than in the Earth's crust, but due to its high density and iron affinity, it has already sunk into the Earth's core when the Earth is in a molten state.

Important features: corrosion resistance, high melting point, silver white

Main producing countries: Brazil, United States, Myanmar, South Africa, Russia, Australia

Important uses: Iridium is commonly used in metallurgy, medicine, automotive industry, electronics, aviation, and other fields. Products such as steel pen tips, compass bearings and scales, surgical instruments, computer storage devices, solid-state lasers, and low thrust rocket engines are all made of this metal. It can even be used to treat cancer, but this material is not suitable for jaw crushers

Most of the practical applications of iridium use its high melting point, high hardness, and corrosion resistance. The consumption of iridium metal, iridium platinum alloy, and osmium iridium alloy is very low, and can be used to manufacture porous spinnerets. A spinneret is used to extrude plastic polymers into fibers, such as rayon. Osmium iridium alloy can also be used for compass bearings and weight scales.

Due to its strong corrosion and high temperature resistance, iridium is highly suitable as an alloy additive. Some long-term components in aircraft engines are made of iridium alloy. At the same time, iridium titanium alloy is also used as a material for underwater pipelines. Adding iridium can improve the hardness of platinum alloys. The Vickers hardness of pure platinum is 56 HV, while platinum alloys containing 50% iridium can have a hardness exceeding 500 HV.

Iridium is also commonly used in instruments that must withstand high temperatures. It is worth mentioning that iridium alloy can resist arc erosion, making it an ideal material for spark plug electrical contacts. Radioisotope Iridium 192 in γ Radiography is an important energy source that facilitates non-destructive testing of metals.

Unmanned spacecraft such as Voyager, Viking, Pioneer, Cassini Huygens, Galileo, and New Horizons all use iridium containing radioactive isotope thermal motors. Due to the high temperature that the thermal motor needs to withstand up to 2000 ° C, the container containing plutonium-238 isotopes is made of both hard and high-temperature resistant iridium. Iridium is also used in X-ray telescopes. The reflector of the Chandra X-ray Observatory has a 60 nanometer thick iridium coating.