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Copper (Cu) and Nickel (Ni), adjacent elements in the periodic system, are closely related and completely miscible. Sometimes called cupronickels, there exists a range of different copper-nickel alloys possessing different properties and useful in a range of different applications. Some of the better known copper nickel alloys include:
- Copper with 10% nickel
- Copper with 30% nickel
- Copper with 25% nickel with 0.05-0.4% manganese
- Copper with 45% nickel (also known as constantan)
All copper nickel alloys consist of only one phase as the copper nickel binary system exhibits complete solid solubility.
Copper-nickel alloy properties vary with composition. Copper 90/10 and Copper 70/30 both show outstanding resistance to corrosion, particularly sea water; however, Copper 70/30 is stronger and has superior resistance to impingement corrosion. On the other hand, a slightly superior resistance to biofouling is exhibited by the 90/10 alloy.
Copper rich alloys are ductile, hardened only by cold working, highly resistant to corrosion, strong and possess a low temperature co-efficient of electrical resistance. The nickel content of these alloys also enables them to retain their strength at elevated temperatures compared with nickel-free copper alloys.
Sea Water Condenser Systems And Desalination Plants
Due to their strong resistance to sea water corrosion, the 90/10 and 70/30 alloys are employed in sea water condenser systems and in desalination plants, as well as in pipe work for chemical plants, offshore oil and gas production and commercial shipping.
As the 90/10 alloy requires no surface protection, hence giving extra safety, it is increasingly employed in brake and hydraulic suspension systems, as well as cooling systems, in cars and commercial vehicles.
Strong resistance to biofouling and sea water corrosion by the 90/10 and 70/30 alloys has led to their use in areas such as cladding for ships’ hulls, legs of oil rig platforms and sea water intake screens.
Copper with 25% nickel and 0.05-0.4% manganese is commonly used for the manufacture of coins, medals and other semi valuable applications.
Due to the very low temperature co-efficient of electrical resistivity, copper-45% nickel alloy is used for resistance wires in high precision resistors. This property allows the resistor to operate at almost exactly the same resistance regardless of temperature.
The copper-45% nickel alloy is also used for thermocouples as it develops a high and uniform EMF when coupled with other metals such as copper and iron.
Copper-nickel alloys may be used in cooling circuits, ammunition, sea water corrosion-resistant assemblies, and condenser tubes. They also have cryogenic applications and can be found in materials used by intensive care units where strong anti-microbial properties are essential to reduce cross-contamination and infections. High levels of aluminum, chromium or tin are introduced to alloys with 30% nickel content for greater resistance to seawater flow, wear and tear, sand abrasion, and galling. These are also used where higher mechanical properties are required.
Sources and Further Reading
This article was updated on the 12th April, 2019.