CuNi 90/10 (C70600) Coil Tube — Copper-Nickel Alloy for Marine Service
Product Overview
The CuNi 90/10 (UNS C70600) Coil Tube is a high-performance copper-nickel alloy product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Composed of approximately 90% copper (Cu) and 10% nickel (Ni) by weight, this alloy represents the gold standard for resistance against seawater erosion-corrosion (also known as flow-induced cavitation corrosion). The coil tube configuration provides exceptional flexibility during installation and heat exchanger assembly, making it an indispensable material in marine engineering, desalination systems, and offshore energy infrastructure.
This product is categorized under the Materials & Metallurgy discipline, specifically within the Copper-Nickel Alloy (CuNi) family of material grades, and is designated as product Item No. 19 in the manufacturer's coil tube catalog.
Material & Properties
The CuNi 90/10 alloy (ASTM/ASME C70600; ISO 6509 CW024A; EN 1.2190) is distinguished by its outstanding resistance to:
- Seawater Corrosion — Exceptional performance in both static and flowing seawater at temperatures up to 50°C (122°F)
- Erosion-Corrosion — Superior resistance to cavitation damage caused by high-velocity seawater flow through heat exchangers and condenser tubes
- Biofouling Resistance — The nickel content inhibits the growth of marine organisms and reduces deposit formation
- Galvanic Corrosion — Compatible with carbon steel and aluminum structures in marine environments
- Ammonia Attack — Not susceptible to stress-corrosion cracking in ammonia-containing environments (unlike brass alloys)
The alloy exhibits excellent formability and weldability, allowing for cold working into thin-walled coil tube geometries without cracking or loss of corrosion resistance. The microstructure is a homogeneous single-phase austenitic solid solution of nickel in copper, which eliminates intergranular corrosion susceptibility.
Specifications
| Parameter | Specification |
|---|---|
| Alloy Designation | CuNi 90/10 (C70600) |
| UNS Number | C70600 |
| Chemical Composition | Cu ≥ 89.0%, Ni 9.0–11.0%, Fe ≤ 2.0%, Zn ≤ 0.5%, Sn ≤ 0.5%, Pb ≤ 0.05%, S ≤ 0.03% |
| Density | 8.9 g/cm³ (8,900 kg/m³) |
| Young's Modulus | 125 GPa (18.1 × 10⁶ psi) |
| Tensile Strength | 345–550 MPa (50–80 ksi), depending on temper condition |
| Yield Strength (0.2% offset) | 170–275 MPa (25–40 ksi) |
| Elongation | ≥ 30% (annealed condition) |
| Thermal Conductivity | 27 W/(m·K) at 20°C |
| Electrical Resistivity | 5.6 μΩ·m at 20°C |
| Maximum Operating Temperature | 50°C (122°F) in seawater; up to 250°C in non-corrosive service |
| Maximum Seawater Velocity | 3.0 m/s (10 ft/s) without erosion-corrosion |
| Corrosion Rate in Seawater | ≤ 0.025 mm/year (0.001 in/year) in flowing seawater |
| Applicable Standards | ASTM B751, ASTM B750, ASTM B151, ASME SA-751, EN 10217, ISO 6509 |
| Product Form | Coil tube (continuous wound coil configuration) |
Manufacturing Process
The production of CuNi 90/10 coil tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage process:
- Alloy Melting & Casting — High-purity copper and nickel are melted in a controlled atmosphere furnace (induction or vacuum arc) to produce a homogeneous ingot. Oxygen content is maintained below 0.002% to prevent oxide inclusions.
- Hot Rolling — The cast ingot is reheated to 900–1050°C and hot-rolled into a semi-finished strip or round bar with controlled dimensional tolerances.
- Intermediate Annealing — Stress relief annealing at 500–650°C eliminates work hardening and restores ductility prior to further cold deformation.
- Cold Drawing / Cold Forming — The semi-finished material is cold-drawn through precision tungsten carbide dies to achieve the final tube dimensions. The coil configuration is achieved by continuous winding on a precision pay-off reel.
- Final Annealing (Solution Treatment) — Tubes are annealed at 750–850°C in a protective atmosphere (argon or vacuum) to achieve the fully annealed (soft) condition, ensuring maximum ductility and corrosion resistance.
- Surface Cleaning & Pickling — Chemical pickling and passivation remove scale, oxide films, and contaminants to ensure a clean, corrosion-resistant surface.
- Dimensional Inspection & Non-Destructive Testing — Each coil undergoes 100% eddy current testing (ECT) for internal and external defects, hydrostatic pressure testing, and dimensional verification per ASTM B751 requirements.
Applications
The CuNi 90/10 coil tube is specifically engineered for demanding marine and offshore applications:
- Marine Heat Exchangers & Condensers — Primary application in shipboard auxiliary condensers, main engine jacket water coolers, and steam turbine condensers where seawater serves as the cooling medium
- Seawater Desalination Pre-Treatment Piping — Used in multi-stage flash (MSF) and reverse osmosis (RO) desalination plants for intake piping, pre-coolers, and heat recovery units
- Offshore Oil & Gas Platforms — Cooling water circuits, ballast water systems, and fire water piping
- Nuclear Power Plants — Secondary loop cooling systems and seawater intake structures (selected applications)
- Naval Vessels & Submarines — Propulsion system coolers, reactor cooling loops, and hull-mounted heat exchangers
- Cooling Towers & Industrial Chillers — In coastal industrial facilities where brackish or seawater cooling is employed
- Marine Ornamental & Architectural Applications — Decorative railings, handrails, and structural elements in coastal environments
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality
- ISO 14001 — Environmental Management System certification
- ASME "S" Stamp — Authorization for pressure-containing equipment materials
- ASTM International — Compliance with ASTM B751/B750 material specifications
- DNV-GL / Lloyd's Register / Bureau Veritas — Classification society approval for marine applications
- Mill Test Reports (MTR) — Full chemical analysis, mechanical properties, and heat traceability provided with each shipment
- NACE MR0175 / ISO 15156 — Suitability for sour service environments (where applicable)
Unique Selling Points
1. Unmatched Seawater Erosion-Corrosion Resistance — The 10% nickel addition creates a protective cupro-nickel oxide film that self-heals under flowing seawater conditions, providing service lives exceeding 10 years without replacement.
2. Coil Configuration Advantage — The continuous coil form eliminates butt welds, reducing potential failure points and installation time by up to 40% compared to straight tube segments.
3. Broad Temperature & Velocity Tolerance — Operates reliably at seawater temperatures up to 50°C and flow velocities up to 3.0 m/s without accelerated degradation.
4. Excellent Fabrication Characteristics — High ductility allows bending, flaring, and U-bend forming without cracking, ideal for complex heat exchanger geometries.
5. Full Traceability & Compliance — Each coil is heat-numbered with complete metallurgical documentation, meeting the stringent requirements of naval architecture and offshore engineering codes.
Technical Notes & Recommendations
- For seawater temperatures exceeding 50°C or highly aerated conditions, consider upgrading to CuNi 70/30 (C70500) for enhanced high-temperature corrosion resistance.
- Welding should be performed using matching filler metal (C70600) with argon gas shielding; post-weld annealing is recommended for critical applications.
- Avoid contact with strong reducing acids (HCl, H₂SO₄) as these will dissolve the protective oxide film.
- Storage should be in a dry, ventilated area away from ammonia-containing substances to prevent surface tarnishing.