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Metal Cobalt

Cobalt is a wear and heat-resistant metal, which determines its use as an alloying additive to steels and alloys in order to improve their properties. It is used also as a material for applying wear-resistant coatings. In addition, this metal is used in permanent magnets due to its high resistance to demagnetization. The page contains description of this metal: physical properties, application areas, grades, and types of products.

Basic information

Cobalt (Co) (Cobaltum) is a chemical element of the VIII group in the periodic table of chemical elements with atomic number 27. It is hard, viscous, shiny, bluish-gray metal that belongs to heavy metals. The density is g/cm, the melting point = 1493 °C, the boiling point 2957 °C. In earth crust, the Co content is 4·10-3% by mass. This metal is part of more than 30 minerals. These include carolite CuCo2S4, linneite Co3S4, cobaltite CoAsS, spherocobaltite CoCO3, smaltite СоAs2, and others. It is approximately (1-7)·10-10% of Co in seawater.


The name of the metal "Cobalt" is closely associated with the Saxon mines, or rather with the underground gnome Kobold, who lived there according to the Saxons. The fact that the ore taken for silver not always gave the precious metal during the smelting. This phenomenon was attributed to the evil deeds of the little gnome Kobold. The ore, which did not give silver, but was very similar by its appearance to silver, was called "Kobold". Most likely, these were Cobalt minerals containing arsenic — cobaltite CoAsS, or Cobalt sulfides — skutterudite, safflorite, or smaltine. In 1735, the Swedish chemist Georg Brandt isolated from this ore a gray with a faint pinkish shade unknown metal, which was called "Kobold" or "Cobalt". Brandt also found that the compounds of this element paint the glass blue.

Cobalt properties

Physical and mechanical properties

Property Value
Atomic number 27
Atomic mass, u 58,93
Atomic diameter, pm 250
Density, g/cm³ 8,9
Specific heat, J/(K·mol) 0,456
Thermal conductivity, W/(m·K) 100
Melting point, °C 1493
Boiling point, °C 2957
Heat of fusion, kJ/mol 15,48
Heat of evaporation, kJ/mol 389,1
Molar volume, см³/mol 6,7
Group of metals Heavy metal

Chemical properties

Property Value
Covalent radius: 130 pm
Ion radius: (+6e) 62 (+4e) 70 пм
Electronegativity (according to Pauling): 2,16
Электродный потенциал: 0
Oxidation degree: 6, 5, 4, 3, 2

Cobalt grades

Modern industry produces several grades of this metal.
  • K0, K1Au, K1A, K1, K2 - metallic Cobalt, the Co content is not less than 99.98% for K0 grade and not less than 98.3% for K2. These grades are available in the form of слитков, cathode sheets, flat bars and plates. Electrolysis or refining is used as the production method.
  • PK-1u - metallic Cobalt containing the specified chemical element Co at least 99.35%. This grade is produced in the form of powder obtained by electrolysis.


  • it has good heat resistance;
  • it has high wear resistance and hardness even at high temperatures;
  • it has a high resistance to demagnetization even at high temperatures and mechanical loads.
  • it has a high cost.


Cobalt in the form of powder is used mainly as an additive to steels. This increases the heat resistance of steel, improves its mechanical properties (hardness and wear resistance at elevated temperatures). This metal is part of the hard alloys that are used to make high-speed tools. One of the main components of the hard alloy is wolfram or titanium carbide. It is sintered in a mixture with a metal Cobalt powder. It is Co that improves the viscosity of the alloy and reduces its sensitivity to pushes and shocks. For example, a cutter made of super-cobalt steel (18% Co) proved to be the most wear-resistant and with better cutting properties compared to cutters made of vanadium steel (0% Co) and cobalt steel (6% Co). Also, Cobalt alloy can be used to protect the surfaces of parts that are subject to heavy loads from wear. Hard alloy can increase the service life of a steel part 4-8 times.

It is also worth noting the magnetic properties of Cobalt. This metal is able to retain these properties after a single magnetization. Magnets must have a high resistance to demagnetization, be resistant to temperature and vibration, and be easily machined. Addition of Cobalt in steel allows them to retain their magnetic properties at high temperatures and vibrations, and also increases the resistance to demagnetization. For example, Japanese steel containing up to 60% Co has a high coercive force (resistance to demagnetization) and only loses its magnetic properties by 2-3.5% during vibrations. Magnetic alloys based on Сobalt are used in the production of electric motor cores, transformers, and other electrical devices.

It is worth noting that Сobalt has also found application in the aviation and space industries. Cobalt alloys are gradually beginning to compete with Nickel alloys, which are well proven and have long been used in this industry. Alloys containing Co are used in engines where a sufficiently high temperature is reached, in aircraft turbine constructions. Nickel alloys lose their strength at high temperatures (at temperatures from 1038°C) and thus lose to Cobalt alloys.

Recently, Cobalt and its alloys have been used in the production of ferrites, as well as printed circuits in radio industry and in the production of quantum generators and amplifiers. Lithium cobalt is used as a highly efficient positive electrode for the production of lithium batteries. Cobalt silicide is an excellent thermoelectric material and allows to produce thermoelectric generators with high efficiency. The Co compounds injected into the glass during boiling provide a beautiful blue (cobalt) color of the glass products.

Cobalt products

Modern industry produces a variety of products from Cobalt. The most common are Cobalt powder, ingots и plates. Cobalt wire is also produced for special purposes.

These products are used in cases where a material with high wear and heat resistance or high resistance to demagnetization is required.


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