Copper-Nickel 90/10 vs 70/30 – Best Marine Alloy 2025 Guide

Copper-Nickel alloys (Cu-Ni) are among the world’s best materials for seawater corrosion resistance. They offer superior performance in challenging marine environments and continue to be among the most reliable choices for desalination plants, offshore systems, marine cooling lines, and high-velocity seawater applications.

They provide:

• Exceptional performance in warm and polluted seawater
• Natural resistance to biofouling
• High mechanical strength
• Excellent heat transfer properties
• Long service life in marine systems

In 2025, the two most widely used Cu-Ni alloys are:
90/10 (C70600) — 90% Copper, 10% Nickel
70/30 (C71500) — 70% Copper, 30% Nickel

Both are outstanding, but choosing the right alloy depends on pressure requirements, temperature, corrosion conditions, and system design. This expert comparison explains which alloy is best for marine, desalination, oil & gas, or heat exchanger projects.

Summary: More nickel = higher strength + better corrosion resistance.
70/30 is stronger & more durable in high-pressure or fast-flowing seawater systems.

Winner for strength → 70/30 Cu-Ni

Cu-Ni 90/10 (C70600)

• Excellent general corrosion resistance
• Ideal for clean seawater
• Performs up to 16 ft/s flow velocity
• Resistant to biofouling

Ideal for: Ship cooling systems, heat exchangers, desalination units

Cu-Ni 70/30 (C71500)

• Superior resistance to high-velocity seawater
• Best for polluted or warm seawater
• Excellent corrosion-erosion resistance

Ideal for: Offshore platforms, submarine piping, high-velocity pump systems

Winner for harsh seawater → 70/30 Cu-Ni
Winner for general seawater → 90/10 Cu-Ni

Both alloys naturally resist biofouling:

• No marine growth
• No algae
• No shell formation inside pipes

Copper-Nickel alloys are preferred in heat exchangers because they:

• Offer excellent heat conduction
• Resist scaling
• Maintain long-term performance

90/10 → Better thermal conductivity
70/30 → Slightly lower conductivity but higher strength

✔ Choose 90/10 Cu-Ni if:

• You need an economical seawater alloy
• Flow velocities are moderate
• The environment is clean seawater
• You need excellent heat transfer

Best For: Commercial ships, desalination plants, general marine cooling

Choose 70/30 Cu-Ni if:

• You need maximum corrosion resistance
• Seawater is polluted or warm
• Flow velocities are high
• System has turbulence or pressure variations
• Long service life is essential

Best For: Offshore platforms, naval ships, subsea equipment

• Excellent seawater corrosion resistance
• Naturally resistant to marine growth
• High mechanical strength (especially 70/30)
• Good heat transfer properties
• Easy to fabricate and weld
• Non-magnetic
• Long service life (20–30+ years)

• Higher cost than carbon steel
• Requires careful welding in thick sections
• 70/30 alloy may be less readily available in some regions