Nickel cathode: properties, grades and applications / Articles

Nickel cathode is a product of electrolytic refining of nickel, obtained by depositing the metal on a cathode base from aqueous electrolyte solutions. It is a key intermediate link in the nickel production chain: ingots are smelted from cathodes, from which rolled products, wire, powders and alloys are then manufactured. It is nickel cathode, with a purity of up to 99.99%, that provides the unique combination of high corrosion resistance, heat resistance, ductility and catalytic activity, thanks to which nickel remains an indispensable material for metallurgy, chemical industry, electrical engineering and battery production.

Chemical Nature and Physicochemical Properties

Nickel (Ni) is a silvery-white transition metal with a characteristic yellowish tint, atomic number 28, atomic mass 58.69 g/mol. The density of nickel is 8.9 g/cm³, melting point — 1455 °C, boiling point — about 2800 °C. Nickel has high ductility, malleability and toughness, and is well suited to mechanical processing, welding and brazing.

A key property of nickel is its exceptional corrosion resistance in alkaline environments, as well as resistance to atmospheric exposure, seawater and many aggressive chemical reagents. A dense oxide film forms on the nickel surface, protecting the metal from further oxidation. Nickel is also characterised by high heat resistance and heat strength, which makes it in demand in the aerospace and energy industries. In addition, nickel has good electrical conductivity and magnetic properties (up to the Curie temperature of about 345 °C).

Nickel is a catalytically active metal, which is used in the chemical industry for hydrogenation, dehydrogenation and other processes.

Classification, Grades and Standards

In Russia and CIS countries, requirements for primary nickel, including cathode nickel, are established by GOST 849-2018 (formerly GOST 849-97) "Primary nickel. Specifications". The standard applies to nickel produced in the form of cathode sheets, strips, plates, ingots, granules and trimmings, and establishes requirements for chemical composition and surface quality.

Depending on the content of nickel and cobalt (Ni+Co), cathodes are divided into grades:

N-0 — the purest grade, Ni+Co content at least 99.99%. Used for critical electrical products, special alloys and scientific research.
N-1u — Ni+Co content at least 99.95%. Used for the production of high-quality alloys and semi-finished products.
N-1 — Ni+Co content at least 99.93%. Widely used in metallurgy for alloying steels and alloys, as well as in electroplating.
N-2 — Ni+Co content at least 99.8%. Used for the production of alloys, battery components and other purposes.
N-3 — Ni+Co content at least 98.6%. Used in metallurgical production and for producing nickel salts.
N-4 — Ni+Co content at least 98.0%. Used in charge materials and for remelting.

Cathode sheets of grades N-0, N-1u and N-1 must have trimmed edges on four sides; salt deposits and oxide hydrates from the electrolyte are not allowed on their surface. For nickel of grade N-2, defects are allowed on an area not exceeding 10% of the surface. Cathodes are packed in bundles tied with steel strip, which ensures ease of transportation and product safety.

Production Technology

Nickel cathode production is based on electrolytic refining. The technological chain begins with the extraction of sulfide copper-nickel ores, their beneficiation and pyrometallurgical processing to produce blister nickel or matte. Anodes are then cast from this raw material and sent for electrolytic refining.

Electrolytic refining is carried out in electrolytic cells filled with a solution of nickel sulfate and chloride. Anodes of blister nickel and cathodes of thin nickel base (blanks) are alternately suspended in the cells. When direct electric current is passed, the anode dissolves, nickel ions pass into the solution and deposit on the cathode, forming a pure nickel deposit. Insoluble impurities (slime) settle to the bottom of the cell and are periodically removed. The cathode current density is 180–270 A/m², and the energy consumption is about 2347–2371 kWh/t.

Modern electrolysis shops use diaphragm cells that separate the anolyte and catholyte, which allows increasing nickel purity and process stability. The resulting nickel cathode, after washing and drying, contains a minimal amount of impurities, which corresponds to the highest world standards. About 30% of world nickel production comes from electrolysis.

Applications

Metallurgy and steel alloying. The main application area of nickel cathode is the production of alloyed, stainless, heat-resistant and acid-resistant steels and alloys. Cathodes are added to the melt as charge when smelting these materials. Nickel increases the strength, corrosion resistance and heat resistance of steels.

Production of nickel alloys. Nickel cathode serves as a feedstock for producing nickel-based alloys (nichrome, monel, inconel, hastelloy, etc.), which are used in aerospace technology, chemical engineering, energy and shipbuilding. These alloys possess exceptional heat resistance and corrosion resistance in aggressive environments.

Electroplating and protective coatings. Nickel cathode is used to prepare electrolytes and anodes in electroplating. Nickel coatings protect machine parts, fasteners, tools and decorative products from corrosion and wear, and also give them a decorative appearance.

Battery technologies. Nickel is a key component of cathode materials for lithium-ion batteries (NMC, NCA), as well as nickel-cadmium and nickel-metal hydride batteries. Growing demand for electric vehicles and energy storage systems stimulates nickel consumption in this segment.

Chemical industry. Nickel is used as a catalyst in hydrogenation, dehydrogenation, hydrotreating of petroleum products and ammonia synthesis. It is also used for the production of alkalis and other chemical products where corrosion-resistant equipment is required.

Other applications. Nickel cathode is used in the production of coins, jewelry, as well as in electrical engineering for the manufacture of wire, strips and contacts.

Safety and Storage

Nickel and its compounds belong to substances of moderate hazard. Nickel dust can cause irritation of the respiratory tract and skin, and prolonged exposure to certain nickel compounds is associated with the risk of sensitisation and carcinogenic effects. When working with nickel dust and fumes, personal protective equipment must be used: respirators, safety goggles, gloves and protective clothing. Premises must be equipped with effective ventilation.

Nickel in massive form (cathodes, ingots) does not present a chemical hazard. Nickel cathode storage is carried out in dry, well-ventilated areas protected from atmospheric precipitation. Cathodes are stacked in bundles and piles while maintaining stability. Joint storage of nickel with oxidizers, strong acids and foodstuffs is not allowed. Under proper storage conditions, nickel retains its properties indefinitely.

Market and Trends

The global nickel cathode market demonstrates steady growth, driven by the development of stainless steel production, batteries for electric vehicles and renewable energy. Nickel remains a strategic metal for the decarbonization of the economy: demand for it is growing from manufacturers of electric vehicles, energy storage systems and wind generators. According to industry estimates, nickel demand in the long term will grow at an outstripping pace compared to supply, due to the limited number of new large deposits and long lead times for capacity commissioning.

Key industry trends include the transition to nickel production with a minimal carbon footprint, the development of laterite ore processing technologies (HPAL), and growing attention to the recycling of nickel-containing materials. The Asia-Pacific region remains the largest producer and consumer of nickel cathode, with significant capacities also concentrated in Russia, Canada, Australia and Europe. Producers with access to quality raw materials and modern refining technologies occupy stable competitive positions.

Conclusion

Nickel cathode remains a fundamental material of modern industry, providing the production of alloyed steels, special alloys, electroplating coatings and battery materials. High purity, corrosion resistance and heat resistance make it indispensable in the context of electrification and the transition to a low-carbon economy. Electrolytic refining technology continues to improve, and requirements for cathode quality and their carbon footprint are constantly increasing. Organising supplies of nickel cathode, including the selection of grade (N-0, N-1, N-2 and others), quality confirmation and logistics, requires an individual approach that takes into account specific technological requirements and operating conditions.