Cupronickel strip

Cupronickel (Sometimes incorrectly written as Cupernickel) or Coppernickel is an alloy of copper, nickel and strengthening impurities, such as iron and manganese. Cupronickel does not corrode in seawater, because its electrode potential is adjusted to be neutral with regard to seawater. Because of this it is used for marine hardware, and sometimes for the propellers, crankshafts and hulls of premium tugboats, fishing boats and other working boats.

A common use is in many silver-coloured modern circulation coins. A typical mix is 75% copper, 25% nickel, and a trace amount of manganes. In the past true silver coins were debased with cupronickel. Despite high copper content the colour of cupro-nickel is silver.

It is used in thermocouples, and a 55% copper/45% nickel alloy is used to make very accurate resistors.

Monel metal is a nickel-copper alloy, containing minimum 63% nickel.