Cobalt is a lustrous, silvery-white metal with a faint bluish tinge. The metal is ferromagnetic up to 1,121 °C (2,050 °F) but is also one of three metals that are ferromagnetic at room temperature. Cobalt, like iron, can be magnetized, and is used where magnetic properties are needed at very elevated temperatures. It is alloyed with Aluminium and Nickel to make particularly powerful magnets.
Cobalt is attacked by oxygen and by water vapour at elevated temperatures, dissolves slowly in dilute mineral acids, does not combine directly with either hydrogen or nitrogen, but will combine, on heating, with Carbon, Phosphorus, or Sulphur.
Among the most crucial applications of Cobalt are its alloys. A relatively large percentage of global Cobalt production is directed to magnetic alloys such as the Alnicos for permanent magnets. Other Cobalt alloys retain their properties at high temperatures, while some Cobalt is directed to superalloys which are used near their melting points (where steels would become too soft).
The metal is also used to create a number of different high performance alloys including hard-facing alloys, tool steels, low-expansion alloys, and constant-modulus (elastic) alloys. In addition to their magnetic properties, Cobalt alloys are also known for being corrosion and wear-resistant, making them suitable for gas turbine generators, aircraft engines and other applications that require high-temperature strength.
Natural Cobalt consists of a stable isotope Cobalt-59, from which the longest-lived artificial radioactive isotope Cobalt-60 is produced. This isotope–Cobalt-60– is used for treatment in cancer therapy (as a tracer and for radiotherapy), in sterilization studies, and in biology and other industries as a radioactive tracer. Gamma radiation from Cobalt-60 has been used frequently in place of X-rays or alpha rays from Radium, towards the inspection of industrial materials to reveal their internal structure, flaws, or the presence of foreign objects. In some countries, this radioactive isotope is also used to irradiate food to preserve it.
Cobalt-based cathode technology has been vital to sustainable technologies, including electric transport and renewable energy storage. Meanwhile, the metal is used a binder in cemented carbides, an essential material for the hard metal industry.
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Cobalt is often used in electroplating because of its attractive appearance, where it hardness and resistance to corrosion to the substrate material it is coated onto. Similarly, Cobalt-Chrome alloys are used in orthopaedic and dental implants due to their biocompatibility, and high corrosion and wear resistance. A more familiar application is the use of Cobalt for centuries to produce brilliant blue colouring as inks and pigments in paint, porcelain, glass, pottery and enamels.
Though it is widely dispersed, Cobalt only makes up 0.001 percent of Earth’s crust. It is found in trace quantities in terrestrial and meteoritic native nickel-iron, and in combination with other elements in natural waters, Ferromanganese crusts deep in the oceans, in soils, and in minerals such as Cobaltite, Linnaeite, Skutterudite, Smaltite, Heterogenite, and Erythrite. With few exceptions, cobalt ore is not usually mined for its cobalt content, instead the metal is recovered as a by-product from the mining of other ores of metals such as Iron, Nickel, Copper, Silver, Manganese, Zinc, and Arsenic. Complex processing is required to concentrate and extract cobalt from these ores.