Seamless Copper Nickel Tube for Heat Exchanger and Marine Water Pipe Applications

Cupronickel 70/30 Seamless Pipe UNS C71500 Heat Exchanger Tube Marine Water Pipe

1.Product Description

Copper-nickel alloy tubes are engineering pipes based on copper with nickel as the primary alloying element. The most widely used commercial grades are C70600 (90-10, approximately 10% nickel) and C71500 (70-30, approximately 30% nickel). Both alloys contain controlled additions of iron (Fe) and manganese (Mn). Iron significantly enhances erosion-corrosion resistance in high-velocity fluids, while manganese serves as a deoxidizer and provides auxiliary strengthening.

The microstructure of copper-nickel tubes is a stable single-phase face-centered cubic (FCC) solid solution, with no risk of phase embrittlement across temperatures from cryogenic up to 300°C, ensuring excellent structural stability. Products are available in seamless form (ASTM B466) and longitudinally welded form (ASTM B467), both manufactured via cold drawing or cold rolling to achieve precision dimensions, clean oxide-free internal bores, and a silver-white metallic surface finish — with higher nickel content producing a whiter appearance. The tubes feature high dimensional accuracy and uniform wall thickness, meeting the design requirements of various heat exchange equipment and pressure piping systems.

2.Product Applications

Leveraging their excellent seawater corrosion resistance and anti-biofouling properties, copper-nickel tubes are widely used in the following five major sectors:

Marine and Shipbuilding — Used as main pipelines for seawater cooling circulation systems, deck firewater ring mains, ballast water treatment system piping, and stern tube cooling lines. They are proven in commercial vessels, naval ships, and offshore platforms.

Power Generation — Serving as steam turbine condenser tube bundles in thermal power plants, auxiliary cooler heat exchange elements in nuclear power stations, fin-tube base pipes in air-cooled condenser islands, and heat transfer tubes in feedwater heaters.

Desalination — Applied in heating section tube bundles of Multi-Stage Flash (MSF) plants, evaporator tubes in Multi-Effect Distillation (MED) plants, and brine heaters, maintaining stable long-term operation under high-temperature, high-salinity conditions.

Offshore Oil and Gas — Used for platform utility piping (seawater, firewater, instrument air), riser external anti-corrosion sheathing, and subsea pipeline anode connection tubes, withstanding severe marine corrosion environments.

General Industry — Including vehicle pneumatic brake tubing, high-purity water and organic solvent transfer piping, chemical piping for weak acids and alkalis, and compressed air system piping.

3.Product Advantages

Superior Corrosion Resistance — In clean seawater, the annual corrosion rate of copper-nickel alloys is only 0.025~0.0025 mm. A dense, adherent oxide/nickel-rich composite protective film forms spontaneously on the surface, continuing to grow during service and possessing self-healing capability — even if locally damaged, the film can re-form within a short period, ensuring long-lasting protection.

Outstanding Biofouling Resistance — Copper ions are continuously released at trace levels into seawater, forming a biostatic layer on the tube wall that effectively prevents attachment and growth of barnacles, algae, mollusks, and other marine organisms. Compared to stainless steel or titanium, systems using copper-nickel tubes can reduce chemical cleaning frequency by over 60%, significantly minimizing downtime for maintenance.

Excellent Mechanical Properties — In the annealed condition, tensile strength ranges from 275 to 345 MPa, yield strength from 105 to 140 MPa, and elongation ≥25%, providing an excellent combination of strength and ductility. The 70-30 alloy offers higher inherent strength for high-pressure applications, and both grades can be further strengthened via cold working (light-drawn or hard-drawn).

Superior Workability and Fabricability — Copper-nickel tubes can be welded using manual TIG welding, orbital welding, oxy-acetylene welding, and brazing. Cold bending performance is excellent, with minimum bend radius as low as 1.5×OD without cracking. Tube ends can be flared, beaded, and mechanically expanded. Compared with austenitic stainless steels, copper-nickel alloys present no risk of stress corrosion cracking (SCC), with minimal grain growth in the weld heat-affected zone, facilitating high-quality weld production.

Outstanding Life-Cycle Economy — Design service life reaches 15~25 years, far superior to carbon steel with plastic coatings. Minimal corrosion allowance is required, allowing for thinner wall thickness design and reduced structural weight. The material is 100% recyclable, aligning with green engineering material development trends.

​4.Key Product Specifications

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