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Copper-nickel uses in marine systems
Copper-nickel alloys, often referred to as CUNI or Cupronickel, have long been a staple material in marine environments, particularly in seawater systems, desalination plants, and offshore infrastructure protection. Copper itself boasts impressive corrosion resistance in atmospheric and freshwater settings, but when combined with nickel, these alloys achieve exceptional performance in harsher conditions like seawater.
Adding nickel to copper enhances its mechanical strength and durability, while also improving its ability to resist both corrosion and erosion in natural aquatic environments—ranging from briny seawater to treated water. Copper-nickel alloys also stand out for their mechanical robustness, showing remarkable resilience against stress corrosion cracking and corrosion fatigue.
These alloys have been trusted by numerous naval fleets and merchant ships since their development over five decades ago. Initially created for use in condensers and piping systems, they’ve consistently demonstrated their reliability across various marine applications. Today, they play a crucial role in offshore oil and gas operations, power generation facilities, and desalination plants. They remain a preferred choice for many vessels due to their time-tested effectiveness.
An additional advantage of copper-nickel alloys lies in their inherent resistance to macrofouling. This characteristic significantly reduces the need for chemical biocides in cooling systems and cuts down on maintenance requirements for offshore platforms and ship hulls, ultimately lowering operational costs.
When it comes to marine-grade copper-nickel alloys, two primary compositions dominate: 90-10 (90% copper, 10% nickel) and 70-30 (70% copper, 30% nickel). Each contains trace amounts of iron and manganese, carefully balanced to optimize performance under high-flow seawater conditions while maintaining strong general corrosion resistance. The 30% nickel alloy tends to be stronger and better suited for high-speed seawater flows, yet the 90-10 variant typically offers sufficient performance at a lower price point, making it more popular for everyday applications. A specialized version of the 30% nickel alloy exists too, featuring 2% manganese and 2% iron. This particular grade is exclusively manufactured as seamless tubes for tube expansion into tube sheets in desalination equipment, eliminating the need for welding. However, care must be taken during fabrication and joining processes because certain impurities could compromise ductility and weldability.
Overall, copper-nickel alloys represent an enduring solution for marine engineering challenges. Their combination of corrosion resistance, mechanical integrity, and practical advantages continues to make them indispensable in modern maritime industries.