Copper-Nickel Bronze (also called Cu-Ni Alloy or Cupronickel) is an alloy primarily composed of copper and nickel, with small additions of iron and manganese to enhance strength and corrosion resistance.
This alloy is known for its excellent resistance to seawater corrosion, biofouling, and stress corrosion cracking, making it one of the most reliable materials for marine, offshore, and heat-exchange applications.
Its unique combination of durability, thermal stability, and anti-corrosive properties makes Copper-Nickel Bronze a preferred choice in industries that operate in harsh, saline, or corrosive environments.
Composition
Exact composition depends on grade, but typical copper-nickel bronze alloys include:
Example Alloy: C67200 (Copper-Nickel-Tin Bronze)
| Element | Typical Range (wt%) | Key Role |
|---|---|---|
| Copper (Cu) | 85–90% | Base metal, corrosion resistance |
| Nickel (Ni) | 5–10% | Enhances strength & corrosion resistance. |
| Tin (Sn) | 1–3% | Improves wear resistance, strength at high temp. |
| Iron (Fe) | ≤0.5% | Adds strength, wear resistance. |
| Zinc (Zn) | ≤0.5% | Slight hardness & strength boost. |
Example Alloy: C84800 (Nickel Bronze)
| Element | Typical Range (wt%) | Key Role |
|---|---|---|
| Copper (Cu) | 80–85% | Corrosion resistance & ductility. |
| Nickel (Ni) | 5–7% | Corrosion & strength enhancement. |
| Tin (Sn) | 2–5% | Wear resistance & strength. |
| Zinc (Zn) | ≤3% | Increased mechanical strength. |
| Iron (Fe) | ≤1% | Wear & strength improvement. |
Mechanical & Physical Properties
Typical Mechanical Properties (Annealed / Wrought)
C67200 (Copper-Nickel-Tin Bronze):
Tensile Strength: ~550–700 MPa
Yield Strength (0.2%): ~300–450 MPa
Elongation: ~18–25%
Hardness: ~80–100 HB
Fatigue Strength: ~250 MPa
Impact Strength: Good ductility.
C84800 (Nickel Bronze):
Tensile Strength: ~480–650 MPa
Yield Strength (0.2%): ~280–420 MPa
Elongation: ~12–22%
Hardness: ~90–120 HB
Fatigue Strength: ~240 MPa
Impact Resistance: Excellent
| Property | Typical Value |
|---|---|
| Density | ~8.7–8.8 g/cm³ |
| Melting Range | ~900–940 °C |
| Thermal Conductivity | ~120 W/m·K at 20 °C (C672) |
| Electrical Conductivity | ~15–20% IACS |
| Coefficient of Expansion | ~19 µm/m·°C |
| Elastic Modulus | ~105 GPa |
Metallurgical Behavior & Strengthening
Solid Solution Strengthening: Nickel and tin atoms dissolve in copper’s matrix and distort the lattice, increasing strength and resistance to deformation.
Intermetallic Enhancements: Small Fe and Ni contributions can form fine stable phases enhancing strength and wear resistance.
Corrosion Resistance Mechanism: Nickel improves the stability of the passive film in seawater and chloride environments, reducing corrosion rates and biofouling.
Refining & Processing Properties
Casting
Copper-nickel bronze alloys have excellent castability, allowing complex components with good dimensional stability and low shrinkage. They fill intricate molds effectively, useful for pump housings, marine fittings, and valve bodies
Forming & Fabrication
Forging & Hot Working: These alloys work well when hot forged for improved grain structure and strength in critical components.
Machining: Good machinability — slightly more challenging than pure copper but manageable with standard bronze tooling thanks to controlled alloy additions (e.g., tin and nickel).
Welding: With preheat and proper technique, many copper-nickel bronze grades can be welded, though some require special techniques.
Available Forms
Bars & Rods — for machining and structural use.
Plates & Sheets — for fabricated components.
Castings & Forgings — for complex shapes.
Discs & Rings — for bearings, couplings, and washers.
Custom profiles — as required for specific industrial parts.
Key Characteristics
| Feature | Benefit |
|---|---|
| Excellent corrosion resistance | Especially in seawater or chloride environments. |
| Good strength & toughness | Suitable for load-bearing components. |
| Wear & abrasion resistance | Enhanced with tin and nickel. |
| Moderate thermal & electrical conductivity | Useful in heat exchangers and conductive parts. |
| Non-magnetic | Useful around sensitive electronics. |
| Biofouling resistance | Reduces maintenance in marine systems. |
| Good fabricability & weldability | Allows complex and large assemblies. |
Applications
Marine & Offshore
Seawater valves, pump bodies, fittings — due to corrosion resistance.
Propeller shafts & drive components — strength and seawater durability.
Marine hardware & fasteners — longevity in saltwater.
Industrial & Mechanical
Bearings, bushings, cams & gears — wear resistance and mechanical strength.
Heat exchanger components & condenser tubes — thermal stability.
Valve seats & stems — corrosion and wear resistance.
Other Uses
Chemical processing equipment — corrosion resistance in aggressive fluids.
Offshore oil and gas platforms — robust structural components.
Advantages & Why Choose Copper-Nickel Bronze?
🔹 Superior Corrosion Resistance
Its performance in seawater and chloride environments outpaces many steels, aluminum, and basic bronzes — reducing maintenance and life-cycle costs
Good Mechanical Performance
Balanced strength, ductility, and fatigue resistance make it suitable for dynamic, load-bearing parts.
Versatile Fabrication
Castable, weldable, and machinable — easy to integrate into complex assemblies.
Stable in Wide Temperature Range
Performs well from low temperatures to moderately elevated service temperatures without losing mechanical integrity
Limitations & Considerations
Cost: More expensive than basic bronzes or brasses due to nickel content.
Machining: Requires proper tooling and parameters; not as free-machining as leaded bronzes.
Conductivity: Lower than pure copper; not suitable where high electrical conductivity is a priority.
Copper-nickel bronze alloys are high-performance copper alloys blending nickel’s strength and corrosion resistance with bronze’s wear resistance and durability. They are especially valuable in marine, industrial, and mechanical applications where seawater exposure, wear, and structural integrity are critical. Their balanced properties, extended service life, and fabrication versatility make them a smart choice for demanding engineering challenges