90/10 Copper-Nickel Buttweld Pipe Fittings
90/10 Copper-Nickel / UNS C70600 / EN CuNi10Fe1Mn (CW352H, 2.0872) — the standard material for seawater piping. Iron-strengthened for impingement and erosion-corrosion resistance in flowing seawater, with natural resistance to marine biofouling. Used in ship and offshore cooling, firewater mains, desalination and condensers. ASME B16.9 and EEMUA 234. EN 10204 3.1/3.2.
½″–24″
Size Range
~3.5 m/s
Max Seawater Velocity
275 MPa
Min UTS (Annealed)
EN 10204
3.1 Std / 3.2 On Req.
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90/10 Copper-Nickel Grade Equivalents
| Common Name | UNS | EN Number | EN Name | Fitting Standard | ASME P-No. |
|---|---|---|---|---|---|
| CuNi 90/10 | C70600 | CW352H (2.0872) | CuNi10Fe1Mn | ASME B16.9 / EEMUA 234 | 34 |
| 90/10 Cupro-Nickel | C70600 | CW352H | CuNi10Fe1Mn | ASTM B466 / B122 (material) | 34 |
Material to ASTM B466 (seamless pipe) / B122 (plate). Fittings dimensionally to ASME B16.9 or to EEMUA 234 for copper-nickel seawater piping. DIN 86019 / MIL-T-16420 also available for naval work.
Chemical Composition — UNS C70600 / EN CW352H
| Element | Specification |
|---|---|
| Cu | Balance (~88.6%) |
| Ni | 9.0–11.0% |
| Fe | 1.0–1.8% |
| Mn | 0.5–1.0% |
| Zn | ≤1.0% |
| Pb | ≤0.05% |
The iron matters. The 1.0–1.8% controlled iron content is what gives 90/10 copper-nickel its resistance to impingement and erosion-corrosion in fast-flowing seawater. Iron below or above the range reduces performance, so mill certification of the iron level is important for seawater service.
Mechanical Properties — CuNi 90/10 (Annealed)
| Min. UTS | Min. YS | Elongation | Max Seawater Velocity | Max Service Temp |
|---|---|---|---|---|
| 275 MPa | 105 MPa | ≥30% | ~3.5 m/s | ~150°C |
Supplied in the annealed condition. Design seawater velocity is limited to about 3.5 m/s for 90/10 (higher for 70/30) to avoid impingement attack; local turbulence at fittings should be controlled by good hydraulic design.
Welding & Post-Weld Heat Treatment
No PWHT Required
Copper-nickel is a single-phase alloy and does not harden on welding, so no post-weld heat treatment is needed. Clean, oxide-free joints and full penetration are essential for seawater service.
Recommended Filler
ERCuNi (AWS A5.7) 70/30-type copper-nickel filler for GTAW and GMAW. Over-alloyed nickel filler ensures weld metal matches or exceeds base seawater resistance.
Preheat
No preheat required. Copper-nickel has lower thermal conductivity than copper, so standard heat input applies. Avoid interpass contamination.
Cleanliness
Remove all oxide, oil and marking ink before welding. Sulphur, lead and phosphorus contamination cause hot cracking in copper-nickel welds.
ASME P-Number
P-No. 34 (copper-nickel alloys). Separate WPS required — not covered by austenitic SS or nickel-alloy procedures.
Selection Guide — 90/10 vs 70/30 Copper-Nickel
| Grade | Nominal Ni | Max Seawater Velocity | Typical Use |
|---|---|---|---|
| CuNi 90/10 / C70600 | ~10% | ~3.5 m/s | Seawater mains, firewater, desalination |
| CuNi 70/30 / C71500 | ~30% | ~4.5 m/s | Pumps, valves, condenser tubes, high flow |
| Super Duplex / S32750 | ~7% | High | High-pressure seawater, no velocity limit |
Key Application Areas
Ship & Offshore Seawater Cooling
Seawater cooling and ballast piping on ships and offshore platforms — the benchmark material for naval and marine seawater systems.
Offshore Firewater Mains
Deluge and firewater ring mains where reliability in stagnant and flowing seawater is critical.
Desalination (MSF & RO)
Brine and seawater piping in multi-stage-flash and reverse-osmosis desalination plants.
Power Station Condensers
Cooling-water circuits and condenser waterboxes at coastal thermal and nuclear power stations.
Heat Exchangers
Tube-side and shell-side seawater heat exchangers benefiting from natural biofouling resistance.
Coastal & Marine HVAC
Seawater-source cooling loops for coastal facilities, ports and marine terminals.
Available Fitting Types — 90/10 Copper-Nickel / C70600
Sizes typically ½″–24″. Larger sizes and EEMUA 234 dimensions available on enquiry.
Elbows — 90° & 45°
Long Radius (1.5D) and Short Radius (1D). ASME B16.9 / EEMUA 234. ½″–24″.
180° Return Bends
Long Radius. ASME B16.9. ½″–12″.
Equal & Reducing Tees
ASME B16.9 / EEMUA 234. ½″–24″.
Concentric & Eccentric Reducers
ASME B16.9 / EEMUA 234. ½″–24″.
Pipe Caps
ASME B16.9 / EEMUA 234. ½″–24″.
Collars / Stub Ends
EEMUA 234 composite flange collars for seawater piping. ½″–24″.
Crosses (4-Way)
ASME B16.9. ½″–8″.
Laterals (45° Y)
ASME B16.9. ½″–8″.
Flanges — All Types
Weld Neck, Slip-On, Blind, composite. EN 1092 / ASME B16.5. C70600. ½″–24″.
Ready to order 90/10 copper-nickel fittings?
Specify size, schedule, fitting type, standard (ASME B16.9 or EEMUA 234), and required MTR level (EN 10204 3.1 or 3.2 TPI). Certified iron content for seawater service on request.
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