Background

Sometimes called cupro-nickels, there exists a range of different copper nickel alloys that possess different properties and hence are suited to 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.
Key Properties

Properties vary with composition, however, some properties are outlined below.

Copper 90/10 and Copper 70/30

· Outstanding resistance to corrosion, particularly sea water

· 70/30 is stronger and has superior resistance to impingement corrosion

· Good resistance to biofouling, with the 90/10 alloy being slightly superior compared to the 70/30 alloy

Copper rich alloys are:

· Ductile

· Can be hardened only by cold working

· Good corrosion resistance

· Good strength

· Low temperature co-efficient of electrical resistance

The nickel content in these alloys also enables them to retain their strength at elevated temperatures compared to copper alloys without nickel.
Applications
Sea Water Condensor Systems And Desalination Plants

Due to the good resistance to sea water corrosion, the 90/10 and 70/30 alloys are employed for sea water condenser systems and in desalination plants, as well as pipe work in chemical plants.
Automotive Applications

Due to the fact that the 90/10 alloy requires no surface protection and hence gives extra safety, this alloy is being increasingly employed for brake and hydraulic suspension systems and cooling systems in cars and commercial vehicles.
Marine Applications

The good resistance to biofouling and sea water corrosion resistance of the 90/10 and 70/30 alloys have lead to its use in applications such as cladding for ships’ hulls, legs of oil rig platforms and sea water intake screens.
Coins

The copper with 25% nickel with 0.05-0.4% manganese is commonly used for the manufacture of coins, medals and other semi valuable applications.
Resistance Wire

Due to the very low temperature co-efficient of electrical resistivity, the copper with 45% nickel alloy is used for resistance wire in high precision resistors. This property allows the resistor to operate at almost exactly the same resistance regardless of temperature.
Thermocouples

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.
Other Applications

Cooling circuits, ammunition, sea water corrosion-resistant assemblies, condenser tubes.