cupronickel

Cupronickel is an alloy of copper and nickel that combines ductility with high resistance to corrosion, particularly in seawater. Commercial grades typically contain about 65–75% copper and 25–35% nickel. Many formulations also include small amounts of iron and manganese to improve strength and fabricability. Two common commercial families are around 70% copper with 30% nickel (often designated CuNi 70/30, such as C70600) and variants that add trace iron and manganese (for example CuNi with Fe/Mn, such as C71500).

Cupronickel exhibits excellent corrosion resistance in seawater, resisting chloride-induced attack and biofouling to a degree greater than many other copper alloys. It forms a stable surface oxide that protects the material, and it maintains toughness and ductility over a wide temperature range. Its electrical conductivity is lower than that of pure copper, and it decreases with increasing nickel content. The alloy welds well with common nickel-containing filler materials and can be cast, extruded, drawn, and formed by conventional methods.

Applications and history: Cupronickel has been used extensively in marine engineering, including condenser tubes, heat exchangers, offshore piping, and desalination equipment. It is also used for some coinage and submerged naval components in certain regions. The alloy was developed in the late 19th to early 20th centuries and was later standardized by international standards bodies as a practical material for environments where seawater exposure is a concern.

Limitations include higher cost relative to pure copper and reduced electrical conductivity compared with copper; its performance depends on precise composition and service conditions.