Cupronickel

Cupronickel is an alloy of copper, nickel and stengthening impurities. It does not corrode in seawater, because its electronegativity is adjusted to be neutral with regard to seawater[?].

Cupronickel is used for marine hardware, and sometimes for the propellers, crankshafts and hulls of premium tugboats, fishing boats and other working boats.

See also bronze (copper alloyed with tin) and brass (copper alloyed with zinc).