Nickel is a versatile metal, widely used in the industrial sector for its corrosion and heat resistance. It is one of the major metals in nickel base alloys and is often added to other metals such as iron or copper in order to enhance their durability and strength in a variety of environments.
The combination of nickel and cobalt makes it an excellent corrosion and oxidation resistant coating material. It is used in a wide range of applications including bolts, fasteners, latches, and springs.
Electrodeposited nickel-cobalt alloy (Ni-Co) coatings are an excellent choice for abrasion resistance, corrosion resistance, and anti-galling properties. They are particularly suitable for fasteners that operate in hazardous environments, and they have been found to reduce hydrogen embrittlement (HE) in connector bolts.
HE is a serious problem in oil and gas industry, where many connections in pumps and valves are at risk of failure. HE is caused by the diffusion of internal hydrogen through the underlying steel bolt.
Ni-Co alloy is a good candidate for the protection of threaded parts, since it can be deposited in thicknesses ranging from 5 um for less corrosive service conditions to >25 um for highly corrosive environments such as marine and industrial settings. The thickness of the deposited coating should be consistent across the entire bolt to ensure uniform protection.
In the past, a nickel-cobalt electrodeposited coating was very common, especially in the USA. It provided the 'bright nickel' effect and was used in a wide range of products. During the period from 1936 to 1969, electrodeposited nickel/cobalt alloys were produced in proportions up to 18%. They contained formate ions and formaldehyde to enhance the brightening and levelling effects of the coating.