Copper-Nickel 70/30: Complete Properties & Application Guide

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What is Copper-Nickel 70/30?

Copper-Nickel 70/30 (UNS C71500) is a cupronickel alloy with excellent resistance to seawater corrosion and biofouling. The 30% nickel content provides higher strength and corrosion resistance compared to 90/10 Cu-Ni, making it ideal for demanding marine applications.

What is the chemical composition of Copper-Nickel 70/30?

The chemical composition of Copper-Nickel 70/30 is carefully controlled to achieve its unique combination of properties and performance characteristics.

Element	Min %	Max %
Copper (Cu)	Balance	Balance
Nickel (Ni)	29.0	33.0
Iron (Fe)	0.40	1.00
Manganese (Mn)	—	1.0
Zinc (Zn)	—	1.0
Carbon (C)	—	0.05
Lead (Pb)	—	0.05

What are the room-temperature mechanical properties of Copper-Nickel 70/30?

The mechanical properties of Copper-Nickel 70/30 vary depending on product form and heat treatment condition. The data below represents typical values for solution-annealed material.

Property	Value
Tensile Strength	380 MPa
Yield Strength (0.2% offset)	125 MPa
Elongation in 2 inches	45%
Density	8.94 g/cm3
Melting Point	1240 °C
Max Service Temperature	300 °C

How corrosion resistant is Copper-Nickel 70/30?

Outstanding resistance to seawater corrosion, including pitting, crevice corrosion, and stress corrosion cracking. Excellent resistance to biofouling due to the natural formation of a protective copper oxide film. Good resistance to ammonia stress corrosion cracking and dezincification.

Where is Copper-Nickel 70/30 used?

The unique combination of properties makes Copper-Nickel 70/30 suitable for a wide range of demanding applications:

• Marine Engineering: Seawater piping, heat exchanger tubing, and condenser tubes.
• Offshore Platforms: Riser systems, ballast water systems, and firewater piping.
• Power Generation: Condenser tubing in coastal power plants.
• Shipbuilding: Seawater cooling systems, heat exchangers, and piping.
• Desalination: Heat rejection and recovery tubing in desalination plants.

Which product forms are available for Copper-Nickel 70/30?

Hangbo Alloy Group manufactures and supplies Copper-Nickel 70/30 in the following product forms, conforming to ASTM, AMS, and ASME specifications:

• Round Bars: Diameters from 6 mm to 300 mm, hot-finished or cold-drawn, solution annealed.
• Seamless Tubes & Pipes: Sizes from 6 mm OD to 219 mm OD, various wall thicknesses.
• Plates & Sheets: Thicknesses from 0.5 mm to 50 mm, hot-rolled or cold-rolled.
• Forgings: Custom flanges, rings, discs, and complex shapes per customer drawing.
• Welding Wire: Diameters 0.8 mm to 5.0 mm, precision-wound coils and spools.

Which standards cover Copper-Nickel 70/30?

Standard	Description
ASTM B111	Condenser Tube
ASTM B466	Seamless Pipe
ASTM B467	Welded Pipe
ASTM B122	Plate, Sheet, and Strip
ASTM B151	Bar and Rod
ASTM B171	Plate

General references: Nickel Institute · AMPP · SAE International · ASTM International

Seawater Performance and Erosion Limits

With 30 % nickel, this grade carries roughly 50 % more strength than 90/10 and tolerates significantly higher water velocities — the reason it is specified for seawater piping, pump bodies and high-duty condenser tubes.

Parameter	Typical value
Tensile strength (annealed)	≈ 480 MPa
0.2 % yield strength	≈ 200 MPa
Corrosion rate, flowing seawater	< 0.02 mm/yr
Max continuous velocity	3.5–4.5 m/s
Impingement / erosion threshold	Higher than 90/10

The alloy also has strong inherent resistance to macrofouling, which reduces cleaning frequency and preserves heat-transfer performance. As with 90/10, avoid galvanic coupling to stainless steel without insulation.

Fabrication and Welding Guidance

• Weld with ERCuNi filler (AWS A5.7 / CuNi30) — never with a copper filler, which gives a weak, corrosion-prone deposit.
• GTAW for root passes and tube work; GMAW or SAW for thicker plate with matching flux.
• Preheat heavy sections to 150–200 °C; keep the joint absolutely free of oil, paint and sulphur.
• Back-purge tube bores with argon; oxidised roots crack during expansion.
• Stress-relieve at 500–550 °C only where service conditions demand it — most marine fabrications are used as-welded.

Frequently Asked Questions

When should I choose 70/30 instead of 90/10?

When flow velocities exceed roughly 3 m/s, when the system sees suspended solids or turbulence, or where higher mechanical strength is needed. The premium is modest against the cost of a premature tube failure.

Is 70/30 resistant to ammonia?

No. Ammonia and ammonium compounds attack copper alloys rapidly — this is the principal reason copper-nickel is excluded from some chemical processes despite excellent seawater behaviour.

What forms does Hangbo supply?

Seamless tube and pipe to ASTM B111 / B466, plate and sheet to B171, plus bar, fittings and flanges with EN 10204 3.1 certification.

What is the chemical composition of Cu-Ni 70/30?

UNS C71500 / W.Nr. 2.0882: copper balance, 29-33% nickel and 0.4-1.0% iron, with manganese and zinc each limited to about 1.0%.

Why is 70/30 used in marine service?

Its higher nickel content gives greater strength and corrosion resistance than 90/10, and the copper-rich oxide film resists biofouling, pitting and crevice corrosion in seawater.

What are its mechanical properties?

Tensile about 380 MPa, yield about 125 MPa and 45% elongation in the annealed condition.

What standards cover Cu-Ni 70/30?

UNS C71500 / W.Nr. 2.0882, with ASTM B111/B466 for condenser and heat-exchanger tube.

What are typical applications?

Seawater piping, condensers, heat exchangers, offshore platform piping and desalination equipment.

How is 70/30 supplied?

Tube, pipe, plate, bar and fittings, with seamless and welded tube as the common service forms.

Contact Us for Copper-Nickel 70/30

Hangbo Alloy Group maintains extensive inventory of Copper-Nickel 70/30 in all standard product forms. We can provide mill test certificates, third-party inspection reports (SGS, TUV), and custom processing services.

For quotations, material certifications, or technical consultation, contact our sales team or call +86 13611656360. We typically respond within 10 minutes.