What is the composition of cupronickel?

In principle, a cupronickel can contain between 1% and 49% nickel, such that copper remains the main element (otherwise you would call it a nickel-copper alloy). Both copper and nickel are completely soluble in each other, which supports this very wide range of compositions.

The most commonly produced cupronickel is the 90/10 (90% Cu, 10% Ni). Increasing the nickel content towards 30% (as found in alloys such as UNS C71640) will increase the abrasion resistance, which will also apply to the flow rates in seawater that parts may be exposed to.

Hiduron 130 (DTD 900/4805, 2.1504) and Hiduron 191 (DEFSTAN 02-835, NES835) both contain c.15% nickel, which is an optimum level to achieve excellent mechanical and physical properties. Both alloys have been used successfully for >50 years since their original development for naval applications, although today they are used in more varied applications such as subsea connectors, valve trim, fasteners and couplings, generally in seawater.

Other Applications for Cupronickel Alloys 

Here are some other applications which require cupronickel alloys –

• Automotive – As the 90/10 alloy requires no surface protection, it is employed more in brake and hydraulic suspension systems plus cooling systems in cars and commercial vehicles.
• Marine – Because of its strong resistance to seawater corrosion and biofouling, the 90/10 and 70/30 alloys are used in areas such cladding for ships‘ hulls, desalination plants, legs of oil rig platforms and seawater intake screens. 
• Coins – Copper with 25% nickel and 0.05-0.4% manganese is used for the manufacturing of coins, medals and other semi-valuable applications.
• Resistance Wire – Cupronickel alloys have a very low-temperature co-efficient of electrical resistivity, meaning they can be used for resistance wires in high precision resistors. This property allows for the resistor to operate at almost the same resistance regardless of the temperature.
• Thermocouples – Cupronickel alloys are used for thermocouples as it develops a high and uniform EMF when it is coupled with other metals like copper and iron.

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