The vital role of copper-nickel tubing in various industries.

Copper-nickel tubing is a specialised piping solution commonly used for the aggressive conditions of marine and saltwater environments. Their excellent resistance to seawater makes them a popular choice in marine applications.

Due to its exceptional corrosion resistance in saltwater, high strength and durability, excellent thermal conductivity, and biostatic properties, it plays a vital role in enhancing operational performance and safety in key industries like shipbuilding, chemical and pharmaceutical processing, desalination plants, offshore structures, and coastal architecture. 

Copper-nickel tubes are commonly found in shipbuilding, in heat exchangers, and in shipping cooling systems.

For all your copper nickel tube needs, get a quote by emailing us at sales@specialmetalalloys.co.uk or call us at +44 (0)7305 752346  or +44 (0)161 278 2386.

Key properties of copper-nickel tubes

• High corrosion resistance and superior performance, especially in marine, chemical, and saltwater environments.
• Outstanding erosion resistance, making copper-nickel tubes highly durable and reliable in marine and industrial environments where exposure to seawater and high-velocity fluids is common.
• Exceptional resistance to pitting and crevice corrosion, ensuring long-term integrity even in harsh and aggressive conditions.
• High strength-to-weight ratio and the ability to maintain structural integrity under high pressure and extreme temperatures, making copper-nickel tubes suitable for demanding applications.
• Its ability to withstand biofouling prevents microbial growth that can impede flow rates, thermal performance, and cause corrosion.
• Robust mechanical properties and inherent resistance to deformation and metal fatigue, which enhance its structural integrity, ductility, and formability, and allow it to withstand high pressures and turbulent flows.
• Excellent thermal conductivity allows it to withstand extreme temperatures and resist scaling under prolonged exposure to heat, and to resist brittle fracture under prolonged exposure to extreme cold.
• It maintains functional electrical properties in wet, high-salinity environments where other conductors like pure copper would oxidise and degrade.
• Its excellent weldability and formability provide significant manufacturing and fabrication benefits and design versatility.
• It is chemically highly compatible with a large variety of metals, elements, and compounds, making it extremely versatile, without unwanted chemical reactions.
• They are available in various sizes, diameters, lengths, and wall thicknesses, depending on application.

Common applications of copper-nickel alloys

• Seawater piping in ships, boilers, cooling systems, fire systems, chemical plants, offshore rigs, power plants, ballast, and bilges.
• Sheathing to protect hulls against biofouling.
• Tubing and components in heat exchangers and condensers, including tubes, tube plates, and baffles.
• Hydraulic lines in offshore oil and gas platforms, processing plants, vehicles, aircraft, and ships.
• Desalination plants and offshore oil rigs for multi-stage and multi-effect distillation, where copper-nickel tubes are valued for their durability and resistance to biofouling.
• Copper-nickel alloys are commonly used in desalination units, commercial and naval shipping, and oil and gas markets, including the gas markets, due to their excellent resistance to seawater corrosion and biofouling.
• Components for HVAC systems used in harsh conditions, including pumps, valves, and fittings.
• Antimicrobial touch surfaces.
• The tubes are typically worked into tube sheets that are used in heat exchangers.

Special Metal Alloys is a global supplier of copper-nickel alloy seamless and welded tubes in fixed lengths or coils.

Let us help you find the best solutions to your copper-nickel tube applications. Contact us for specialist advice and competitive prices. 

Get a quote: email us at sales@specialmetalalloys.co.uk or call us at +44 (0)7305 752346  or +44 (0)161 278 2386.

Want to know more?

Chemical composition of copper-nickel tubing

The addition of nickel significantly increases its strength and enhances copper’s corrosion resistance. In certain grades, small quantities of iron and manganese are also added to improve strength and durability further, and to form a resilient protective film on the surface of the tubes.

 While the specific composition of copper-nickel tubing depends on the intended use, the two main grades are 90/10 and 70/30 ratios of copper and nickel.

Due to its exceptional resistance to stress and cracking erosion, 90/10 excels in applications where high durability is of primary importance, while 70/30 is renowned for its superior resistance to seawater and biofouling.

80/20 copper-nickel is a less common grade that provides the middle ground between 90/10 and 70/30 in higher water velocities and corrosive environments. A special grade like C71640 (66-30-2-2) is a robust alloy specifically designed for high-velocity seawater and environments with suspended solids.

Should you use seamless or welded copper-nickel tubing?

In summary, due to its inherent uniformity and lack of seams, you should use seamless tubing for the absolute highest performance and reliability in harsh conditions, whereas welded tubing is often the better choice for cost-effective general use.

Seamless tubes are stronger, can withstand greater pressure and stress, and are more corrosion resistant because they are extruded and drawn from a single, solid, uniform billet. This makes them better for critical applications under high pressure, temperatures, stress, and extreme corrosion.

Welded tubes are formed from a rolled flat strip and welded along the seam. While they are not as strong, they are generally cheaper and available in longer lengths. They are usually more economical for general, non-critical applications, where longer continuous lengths are required.

What are the main differences between seamless and welded copper-nickel tubes?

• Seamless tubing:

o   Produced from solid billets without any seams.

o   Uniform strength that generally makes it stronger and more pressure resistant.

o   No weak areas that are exposed to corrosion.

o   Usually more flexible, with better ductility and thermal conductivity.

o   Better suited to marine applications exposed to extreme conditions.

o   Usually more expensive.

o   Welding and further processing can be more complex than for welded tubing.

• Welded tubing:

o   Created from flat sheets rolled and welded together.

o   Strength varies according to the consistency of the weld, with potential weak spots, and pressure resistance can be compromised.

o   Good corrosion resistance, but unless specifically alloyed, the welded joint could be less resistant to corrosion.

o   Flexibility might be affected by the welded seam, and the thermal conductivity and ductility are generally less than that of seamless tubing.

o   Better suited to general applications in various industries.

o   It is generally more cost-effective in less extreme conditions.

o   It can usually be welded and further modified.

Advantages of using copper-nickel seamless tubes

• They are designed to meet specific technical requirements in harsh marine and industrial environments.
• Seamless copper-nickel tubes are hard, offering exceptional durability and strength, making them ideal for demanding environments where resistance to pressure, heat, and corrosion is critical.
• Its high tensile strength and durability make it highly suitable for marine environments, desalination plants, coastal and offshore power generation, offshore drilling, oil and gas processing and transportation, and defence applications.
• Because of its high yield strength, it can withstand significant stress without deformation.
• Its weldability, formability, and ductility allow for easy bending, shaping, drawing, and welding, without compromising structural integrity or corrosion resistance.
• Its excellent ductility, thermal and electrical conductivity, and thermal resistance all contribute to its versatility in almost any industry.
• The copper-nickel alloy creates an inherent resistance to erosion, seawater corrosion, and extreme temperatures.
• In addition to its inherent corrosion resistance, it forms a protective oxide film that shields the surface from corrosive elements. This increases the corrosion resistance, eliminates the need for additional coatings and reduces maintenance requirements.
• They are inherently resistant to microbial growth and other forms of biofouling, including inorganic, calcareous and non-calcareous growth or attachment to the surface.

The two most common grades of copper-nickel tubing

• 90/10 CU-Ni (C70600) (90% copper and 10% nickel)
  • It is a budget-friendly marine option, and is a cheaper option that is more popular in the market due to its widespread use and cost-effectiveness. 
  • It offers a very good balance of mechanical properties, thermal conductivity, formability, and corrosion resistance.
• 70/30 CU-Ni (C71500) (70% copper and 30% nickel)
  • It offers superior
    • strength and corrosion resistance, particularly in aggressive marine environments.
    • resistance to impingement corrosion at higher fluid velocities, such as experienced in naval vessels and offshore applications.

Industry standards for copper-nickel tubing

Rigorous, standardised industry specifications ensure the quality, reliability, safety, and performance criteria, detailing chemical composition, mechanical properties, and manufacturing processes and standards.

ASTM B466, ASTM B467, and ASME SB466 each establish distinct requirements for performance in marine environments, and manufacturers and suppliers must adhere to these stringent standards when delivering copper-nickel tubes to contractors and end users.

How are copper-nickel tubes manufactured?

The stringent process starts with melting copper, nickel, and any additional alloying elements, such as iron and manganese, in precise ratios in a furnace.

The molten metal is cast into either billets (for seamless tubes), sheets (for welded tubes), or slabs.

Further processing could be either hot or cold working steps to obtain the exact shape and dimensions required for their intended applications. The main differences between the two processes are:

Cold working:

• Because it is usually done at room temperature, where recrystallisation does not happen, it requires a very high force.
• This process increases the yield and tensile strength, hardness, and fatigue resistance.
• The grain structure is stretched, and internal stresses are introduced, potentially leading to reduced ductility and dimensional instability.
• It produces a smoother and brighter surface, with superior dimensional accuracy and tight tolerances.
• Due to the risk of cracking, only limited deformation is possible, and for further shaping, the metal first requires annealing.

Hot working:

• Hot working is usually done between 850 -1025°C, which is above recrystallisation temperature, requiring much less force than for cold working.
• This process makes the metal more malleable and increases ductility and toughness.
• Due to simultaneous deformation and recrystallisation, the grain structure remains uniform, with uniform stress distribution and consistent strength and hardness, with greater safety and design possibilities.
• Scale formation and oxidation often lead to a poorer surface finish.
• It is possible to deform the metal to a much larger degree in a single pass, without the risk of cracking.

What is annealing?

Metal is heated to a specific temperature, held, and then slowly cooled to soften it, relieve internal stresses, increase ductility, and improve workability. Annealing makes the microstructure of the metal more stable, causing it to be less brittle and easier to shape, bend, or form without cracking.

How is seamless tubing manufactured?

Hot-rolling

o   Round billets, heated to about 1300 °C, are pierced along their axis with a cone-shaped plug or a mandrel, while being cross-rolled between rollers (hot-rolled), creating a hollow shell.

o   The shell is stretched, and its walls are thinned using rollers until it reaches the required length and thickness.

o   Several rolling stages accomplish the eventual dimensions, and the tubes are straightened to remove any warps.

Extrusion

o   Heated billets are pierced and forced through a series of dies to achieve their desired diameters and wall thickness.

o   The die opening forms the outer profile, while a mandrel forms the inner profile, producing a seamless tube with uniform wall thickness.

o   This process is followed by passing these tubes through several rolling stages, or cold drawing the tube through dies to achieve precise dimensions.

o   Extrusion is typically used for complex shapes or high-strength alloy tubes that are difficult to roll.

How is welded tubing manufactured?

• Flat metal strips of the right thickness are cut into the required width and rolled into cylindrical shapes.
• The two edges are lined up and fused by specific welding techniques, including:
  • High-frequency (electric resistance) welding, often with a rotating electrode. This process is used for general-purpose tubing.
  • Copper-nickel tubes and other alloys are often welded with a laser beam for precise welding.
  • Gas tungsten arc welding uses a non-consumable tungsten electrode to produce high-quality welds in stainless steel.
  • Submerged arc welding is used for thick-walled tubes, usually in a spiral or longitudinal weld pattern.
  • The weld bead is usually removed and smoothed. Sometimes the weld is treated by annealing to improve its stress and corrosion properties.

Factors to consider when choosing copper-nickel tubing

Chemical compatibility

Using materials that react with copper-nickel tubing will compromise the corrosion resistance and lead to premature failure.

High pressure

The inherent strength and durability of copper-nickel tubes ensure they can perform reliably under high pressure in saltwater, provided the correct grades, diameter and wall thickness are chosen.

Temperature

Understanding the operating temperatures will ensure that the correct grade and sizes are selected to optimise the formation of the protective film, corrosion resistance, and mechanical strength of the copper-nickel tubes.

At high temperatures, the mechanical strength and ductility are reduced, while the protective film develops faster.

Grades like 90/10 and 70/30 are better suited to maintain their structural integrity and corrosion resistance at wide temperature ranges.

Copper-nickel tubes vs marine-grade stainless steel

Each material has been engineered for specialised applications, offering distinct properties and performance characteristics. Choosing the right option depends on the specific requirements of your project. Both copper-nickel and marine-grade stainless steel are widely used in plumbing, though under different conditions.

• Copper-nickel tubes
  • Excel in demanding saltwater environments and outperform stainless steel and brass in these environments, thanks to their outstanding resistance to seawater corrosion, biofouling, and stress corrosion cracking. 
  • Their non-magnetic nature also makes them ideal where magnetic interference with wiring or electronics must be avoided.
  • They are commonly used in industrial applications such as power generation, where both high-strength and exceptional corrosion resistance are required.
  • While generally more costly than marine-grade stainless steel, copper-nickel can prove more economical compared to premium super duplex alloys.
  • Common applications for which copper-nickel is preferred include piping systems, heat exchangers, components exposed to aggressive marine conditions, and in stagnant saltwater.
• Marine-grade stainless steel
  • Provides excellent strength, temperature tolerance, and rust resistance. 
  • It is generally better suited for chemical or acidic environments and for projects requiring high structural strength. 
  • Its superior weldability often simplifies installation.
  • Typical uses where marine-grade stainless steel is preferred include structural components, handrails, fasteners, and parts exposed to harsh chemicals.
  • Both materials demand minimal maintenance, though stainless steel may require more frequent cleaning to prevent staining.

When should you use carbon steel tubes instead of copper-nickel?

Carbon steel tubes offer a more economical solution for general high mechanical strength structural or high-pressure applications, which do not require the exceptional corrosion resistance, thermal conductivity, ductility, and malleability of copper-nickel.

What to look for in a special metal supplier

• Quality certifications such as ISO 9001, ASTM, ASME, or certifications specific to your industry.
• Certification of the exact composition and properties of the grades and materials used, and Mill Test Certificates to trace the tubes back to their origin.
• Availability of copper-nickel tubes in both fixed lengths and coils, with coils offered for certain compositions like 90/10 but not for others, such as 70/30.
• A strong supplier presence and expertise in the UK, ensuring local industry knowledge, manufacturing standards, and reliable regional availability of copper-nickel tubes and related products.
• A solid reputation and experience in ethical practices, and reliably supplying special metals to various industries.
• Technical expertise on chemical composition, material behaviour and performance qualities, to guide material selection, design consultation, and downstream processing, and fabrication.
• Quality control and the ability to perform testing with spectrometers, tensile testing machines, and NDT (non-destructive) equipment, either in-house or by trusted third-party facilities.

Special Metal Alloys ticks all these boxes. By doing business with us, you are assured of the best quality, technical support, and service.

Get in touch

Contact us online, or give us a quick call at +44 [0]161 278 2386 to find out more.