CuNi

CuNi refers to a family of copper-nickel alloys composed primarily of copper with zinc? No, copper with nickel. The nickel content typically ranges from about 10 to 40 percent, with the remainder copper. The most common commercial grades are CuNi around 70/30 (70% copper, 30% nickel) and CuNi around 90/10, though variants exist with intermediate compositions.

These alloys are renowned for their excellent resistance to corrosion in seawater and many aggressive environments, along with good ductility and formability. They maintain strength at elevated temperatures better than pure copper and have relatively low magnetic permeability. Their corrosion resistance is largely due to the nickel-rich surface film that forms in chloride-containing media, reducing uniform and local attack and mitigating biofouling in some cases. Thermal conductivity is lower than that of pure copper but higher than many stainless steels, and mechanical properties improve with cold working.

Fabrication and processing options include casting and wrought processing (hot and cold working). They are typically readily machinable and weldable by conventional methods; post-weld heat treatment is often used to restore or enhance ductility after fabrication. Cold working increases strength but reduces ductility, while solution annealing can restore ductility and relieve stresses.

Applications span marine engineering and energy systems, including condensers, heat exchangers, piping, and seawater equipment. CuNi alloys are also used in desalination plant components and certain components exposed to corrosive environments. They are found in some coinage and decorative items as well. While relatively expensive and heavier than some alternatives, their sustained corrosion resistance in seawater remains a primary advantage.