Cupronickel (also known as copper-nickel) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese. Aside from the terms cupronickel and copper-nickel, several other terms have been used to describe the material: the tradenames Alpaka or Alpacca (registered trademark), Argentan Minargent, and the French term, Cuivre blanc, are still registered; cupronickel is also occasionally referred to as "hotel silver," plata alemana (Spanish for "German silver"), "German silver," and "Chinese silver".〔Deutsches Kupfer-Institut (Hrsg.): ''Kupfer-Nickel-Zink-Legierungen''. Berlin 1980.〕
Cupronickel is highly resistant to corrosion in seawater because its electrode potential is adjusted to be neutral with regard to seawater. Because of this, it is used for piping, heat exchangers and condensers in seawater systems, marine hardware, and sometimes for the propellers, crankshafts and hulls of premium tugboats, fishing boats and other working boats.
A common consumer use of cupronickel is in silver-coloured modern-circulated coins. A typical mix is 75% copper, 25% nickel, and a trace amount of manganese. In the past, true silver coins were debased with cupronickel.
Thermocouples and resistors whose resistance is stable across changes in temperature contain the 55% copper-45% nickel alloy constantan.
Monel metal is a nickel-copper alloy, containing a minimum of 63% nickel.
Despite its high copper content, cupronickel is silver in colour.
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