Copper Nickel

Copper-nickel (often called “cupronickel” or “CuNi”) is a family of copper-based alloys containing nickel as the primary alloying element, typically along with small additions of iron and manganese for strength and stability.

Common Grades:
The two most widely used compositions are:

1. 90/10 CuNi (approx. 88% Cu, 10% Ni, 1.5% Fe, 0.5-1% Mn) – UNS C70600
2. 70/30 CuNi (approx. 70% Cu, 30% Ni, 0.5-1% Fe, 0.5-1% Mn) – UNS C71500

These are governed by standards such as ASTM B111, B466, B467 (tube and pipe), and ASME SB-111/SB-466/SB-467 for pressure applications, with equivalents referenced under DIN, EN, and ISO systems depending on the product form.

Key Properties:
1. Excellent seawater corrosion resistance: this is the alloy’s defining characteristic
2. Strong resistance to biofouling (marine organism attachment on surfaces)
3. Good resistance to erosion-corrosion, even in high-velocity seawater flow
Good weldability and formability
4. Moderate strength: not a structural or high-strength alloy; nickel here is for corrosion resistance, not mechanical performance like in nickel alloy steels

Typical Applications:
Because of its seawater performance, copper-nickel is heavily used in:

1. Marine and offshore piping systems (seawater cooling, ballast, firefighting lines)
2. Shipbuilding (hull cladding, condenser and heat exchanger tubing)
3. Desalination plants
4. Power plant condensers using seawater or brackish water cooling
5. Offshore oil & gas platforms (seawater service piping)

Important Distinction for Sourcing:

Copper-nickel is a copper alloy, not a steel grade; it sits outside carbon, stainless, and alloy steel classifications, even though it’s often specified alongside steel in the same marine, offshore, and petrochemical projects (e.g., a project might call for 90/10 CuNi piping alongside 316L stainless steel fasteners and duplex steel fittings). Buyers sometimes group it under “corrosion-resistant alloys” (CRA) in project specifications rather than under steel.

If you’re sourcing it for a project spec, the key details to confirm are: exact grade (90/10 vs 70/30), product form (pipe, tube, sheet, rod), applicable standard (ASTM/ASME/EN), and whether mill test certification (e.g., EN 10204 3.1) is required – the same certification framework used for steel round bars.