What is Cupro-Nickel 90/10? Properties, Uses & Specifications

Introduction

Cupro-Nickel 90/10 (also known as CuNi 90/10 or by its UNS designation C70600) is a copper-nickel alloy containing approximately 90% copper and 10% nickel. It is one of the most widely used corrosion-resistant alloys for seawater and marine applications.

This guide covers everything you need to know about CuNi 90/10 — from its composition and properties to its applications and the standards it must meet.

Chemical Composition

Cupro-Nickel 90/10 (UNS C70600):

•Copper: Balance (~88%)

•Nickel: 10–11%

•Iron: 1.0–1.8%

•Manganese: 1.0% max

•Zinc: 0.5% max

•Lead: 0.02% max

•Carbon: 0.05% max

•Sulfur: 0.02% max

The addition of iron (1-1.8%) is crucial — it dramatically improves the alloy's resistance to impingement attack and erosion-corrosion in flowing seawater, which is why iron content is carefully controlled.

Properties

Mechanical Properties:

•Tensile Strength: 275 MPa min (annealed)

•Yield Strength: 105 MPa min

•Elongation: 30% min

•Hardness: 100-140 HB

•Density: 8.94 g/cm³

Key Characteristics:

•Excellent resistance to seawater corrosion and biofouling

•Good resistance to stress corrosion cracking

•Inherent antimicrobial properties (copper ions inhibit marine organism attachment)

•Good thermal conductivity for heat exchanger applications

•Low macrofouling rate — marine organisms don't easily attach

•Good weldability with both TIG and MIG processes

•Can be readily fabricated using standard copper working techniques

Marine and Industrial Applications

CuNi 90/10 is the material of choice for seawater systems:

Marine Applications:

•Seawater piping systems on ships and offshore platforms

•Desalination plant condenser and heat exchanger tubes

•Seawater cooling systems

•Offshore platform firewater systems

•Ship hulls and propellers (biofouling resistance)

•LNG plant seawater intakes

Industrial Applications:

•Power plant condenser tubes

•Chemical process heat exchangers

•Hydraulic brake lines

•Fresh water piping in coastal installations

Why not just use stainless steel? While SS 316 has good general corrosion resistance, CuNi 90/10 has better biofouling resistance, is more resistant to crevice corrosion in low-velocity seawater, and doesn't suffer the same microbiologically influenced corrosion (MIC) issues as stainless steel.

Applicable Standards

CuNi 90/10 products are manufactured per these standards:

Pipes:

•ASTM B466 / ASME SB466 — Seamless Copper-Nickel Pipe

•ASTM B467 — Welded Copper-Nickel Pipe

Tubes:

•ASTM B111 / ASME SB111 — Copper-Nickel Heat Exchanger & Condenser Tubes

•ASTM B552 — Copper-Nickel Tube (general service)

Fittings:

•ASME B16.22 — Wrought Copper and Copper Alloy Fittings

•MSS SP-104 — Wrought Copper Solder Joint Pressure Fittings

Flanges:

•ASME B16.24 — Copper Alloy Pipe Flanges

Starlight Tubes supplies CuNi 90/10 pipes per ASTM B466, tubes per ASTM B111, and fittings per ASME B16.22 with full Mill Test Certificates.

CuNi 90/10 vs 70/30 — When to Choose Which

CuNi 90/10 (C70600):

•Lower cost than 70/30

•Adequate for most seawater systems

•Standard choice for seawater piping up to 3.5 m/s flow velocity

•Typical for ship seawater systems, coastal power plants

CuNi 70/30 (C71500):

•Higher nickel content → better corrosion resistance

•Handles higher flow velocities (up to 4.5 m/s)

•Better for highly polluted or high-temperature seawater

•Used in condenser tubes for coastal/nuclear power plants

•Higher cost (roughly 30-50% more than 90/10)

Rule of thumb: Use 90/10 as your standard choice; upgrade to 70/30 only if the seawater conditions are particularly aggressive or flow velocities exceed 3.5 m/s.

Frequently Asked Questions

Q.What is Cupro-Nickel 90/10 used for?

CuNi 90/10 (C70600) is primarily used in seawater and marine applications including ship seawater piping systems, desalination plant condenser tubes, offshore firewater systems, heat exchangers, and power plant cooling systems. Its excellent resistance to seawater corrosion and biofouling makes it the preferred material for these applications.

Q.What is the difference between CuNi 90/10 and 70/30?

CuNi 90/10 (C70600) contains 10% nickel while 70/30 (C71500) contains 30% nickel. The higher nickel content in 70/30 provides better corrosion resistance and can handle higher seawater flow velocities (up to 4.5 m/s vs 3.5 m/s). However, 70/30 costs 30-50% more. Use 90/10 as the standard choice and upgrade to 70/30 for aggressive conditions.