Copper-nickel or Cupronickel, as it is commonly known is an alloy of copper and nickel. Other elements such as iron and manganese is added to Cu-Ni to give it additional strength. Cupronickel is highly resistant to sea-water corrosion. Copper nickel produces a layer of oxide on its surface when exposed to seawater, which protects it from corroding. Other properties of Cu-Ni include resistance to macrofouling, ductility, tensile strength, corrosion resistance, and thermal conductivity.
The excellent ductility of Copper-nickel makes it formable in various forms for different purposes. Cupronickel finds applications in armaments manufacturing, coin and medal minting, desalination plants, marine engineering, petrochemical plants, chemical plants, and electricity generation. Other applications include propellers, crank-shafts, hulls of tugboats, medical equipment, automobile parts, jewellery and fishing boats. The combination of ductility retention and thermal conductivity makes it usable in cryogenic applications. Cu-Ni products also do not execute ferromagnetism. Cupronickel is most commonly used for coin minting, as has replaced the traditional silver coins. The modern-circulating coins are made from copper-nickel.