Cobalt

Cobalt is a chemical element with the symbol Co and atomic number 27. It is a hard, silvery-gray transition metal that is ferromagnetic near room temperature and resistant to corrosion. Cobalt has a high melting point of 1495 C and a boiling point of about 2927 C, and natural cobalt is composed primarily of the stable isotope 59Co. In chemistry, cobalt most commonly exhibits oxidation states of +2 and +3, forming salts such as cobalt(II) chloride and cobalt(III) oxides.

Cobalt occurs in several mineral forms, including cobaltite (CoAsS), erythrite, skutterudite, and smaltite, and is usually obtained as a byproduct of copper and nickel mining. Globally, the Democratic Republic of the Congo, Russia, Canada, and Zambia are important producers. After mining, cobalt is refined by smelting and electrolytic processes to produce metal, powders, and alloys.

Major uses of cobalt include alloy production, particularly in high-strength steels, superalloys for turbine engines, and hard wear-resistant materials. Cobalt is also an essential component of many rechargeable battery cathodes, especially lithium cobalt oxide (LiCoO2) in older lithium-ion batteries. Cobalt-containing magnets and catalysts are widely used, and cobalt is a well-known pigment in glass and ceramics, producing the characteristic cobalt blue. Cobalt-60, a radioisotope produced in reactors, is used in medical radiotherapy and industrial radiography.

Historically, cobalt was named after kobold, a German word for a goblin, reflecting ore impurities that hampered early smelting. The element was isolated in the 18th century by Georg Brandt. Today, concerns about supply chains and ethical sourcing accompany the use of cobalt in batteries. Toxicity can arise from cobalt compounds through inhalation or ingestion; exposure may affect the lungs, heart, and thyroid, and occupational safety measures are required to limit risk.