Cu-Ni 90/10 (C70600) & 70/30 (C71500) grades. ASTM B564 / ASME SB564, ASME B16.5 / B16.47. The gold standard for seawater piping, marine systems, and desalination — outstanding corrosion resistance, biofouling resistance, and erosion resistance in the most demanding wet environments. Exporting to 65+ countries for 30+ years.
Cupro nickel (Cu-Ni) flanges are copper-nickel alloy piping components engineered for one of the most demanding service environments in the world: seawater. Used across marine, offshore, desalination, naval, and coastal power generation industries, Cu-Ni flanges are the universal specification for seawater cooling, firewater, ballast, and produced-water piping systems where carbon steel or stainless steel would fail prematurely.
Tesco Steel & Engineering manufactures cupro nickel flanges in 90/10 (UNS C70600) and 70/30 (UNS C71500) grades — as well as the high-iron variant UNS C71640 — to ASTM B564 / ASME SB564, dimensioned per ASME B16.5, B16.47, EN 1092-1, and DIN standards. Available in all types: weld neck, blind, slip-on, socket weld, lap joint, threaded, long weld neck, and spectacle blind.
Every Cu-Ni flange is supplied with EN 10204 3.1 material test certificates, chemical & mechanical test reports, and optional third-party inspection. Weld qualification records using ERCuNi (AWS A5.7) filler are available on request.
90% copper, 10% nickel. The most widely used Cu-Ni grade for seawater piping. Excellent general seawater corrosion resistance, good biofouling resistance, and outstanding value. UTS ~275 MPa, YS ~100 MPa. Rated for seawater velocities up to ~1.5 m/s.
View 90/10 Flanges →70% copper, 30% nickel. Higher strength (UTS ~380 MPa), better elevated-temperature performance, and superior resistance in high-velocity seawater (up to ~3.5 m/s). Preferred for demanding offshore, naval, and desalination applications.
View 70/30 Flanges →Enhanced iron content (1.7–2.3% Fe) dramatically improves erosion-corrosion resistance in high-velocity seawater beyond what standard 70/30 achieves. Ideal for pump casings, condenser water box connections, and high-flow desalination headers.
View C71640 Flanges →The key to cupro nickel's exceptional seawater performance lies in its composition — particularly the iron and manganese additions, which are critical for erosion-corrosion resistance and formation of the protective surface film.
| Element | 90/10 — C70600 | 70/30 — C71500 | Role in Performance |
|---|---|---|---|
| Copper (Cu) | Balance (≥ 86.5%) | Balance (≥ 63.0%) | Base metal; provides natural seawater corrosion resistance and biofouling inhibition |
| Nickel (Ni) | 9.0 – 11.0% | 29.0 – 33.0% | Primary alloying element; increases strength, seawater resistance, and elevated-temperature performance with increasing content |
| Iron (Fe) | 1.0 – 1.8% | 0.40 – 1.0% | Critical — dramatically improves erosion-corrosion resistance in flowing seawater; strengthens protective oxide film |
| Manganese (Mn) | ≤ 1.0% | ≤ 1.0% | Improves hot workability during forging; strengthens the protective corrosion film |
| Lead (Pb) | ≤ 0.02% | ≤ 0.02% | Strictly controlled — even trace Pb causes dezincification-type attack in seawater |
| Zinc (Zn) | ≤ 0.50% | ≤ 0.50% | Kept low — zinc additions reduce seawater corrosion resistance |
| Carbon (C) | ≤ 0.05% | ≤ 0.05% | Very low — prevents carbide precipitation and preserves ductility |
| Sulfur (S) | ≤ 0.02% | ≤ 0.02% | Minimised — sulfur contamination causes hot cracking during welding |
| Property | Cu-Ni 90/10 (C70600) ✦ | Cu-Ni 70/30 (C71500) | Cu-Ni C71640 |
|---|---|---|---|
| Tensile Strength (UTS) | ≥ 275 MPa (40 ksi) | ≥ 380 MPa (55 ksi) | ≥ 415 MPa (60 ksi) |
| Yield Strength (0.2% offset) | ≥ 100 MPa (15 ksi) | ≥ 125 MPa (18 ksi) | ≥ 170 MPa (25 ksi) |
| Elongation (min) | ≥ 30% | ≥ 30% | ≥ 20% |
| Hardness (approx) | ~65 HRB | ~70 HRB | ~75 HRB |
| Density | ~8.9 g/cm³ | ~8.95 g/cm³ | ~8.9 g/cm³ |
| Melting Range | ~1100–1145°C | ~1170–1240°C | ~1170–1230°C |
| Max Service Temp (B16.5) | ~232°C (450°F) | ~260°C (500°F) | ~260°C (500°F) |
| Seawater Velocity Limit | ~1.2–1.8 m/s | ~2.5–3.5 m/s | ~3.5–4.5 m/s |
| Primary Application | General marine seawater piping | High-velocity seawater, naval, desalination | High-erosion seawater, condenser connections |
No other engineering alloy at comparable cost combines all five seawater performance properties that Cu-Ni delivers simultaneously:
Cu-Ni alloys develop a thin, stable, self-repairing cuprous oxide–hydroxychloride protective film in seawater within hours. This film is strongly adherent, electrically resistive, and naturally resistant to chloride attack — the corrosion mechanism that destroys carbon steel and stress-corrodes austenitic stainless steel.
The copper ion release from Cu-Ni surfaces is naturally toxic to marine organisms — barnacles, mussels, tube worms, and biofilm cannot colonise Cu-Ni piping. This eliminates biological fouling that causes flow restriction, accelerated corrosion under deposits (MIC), and blockage in seawater systems. No biocide injection needed.
The iron addition in Cu-Ni (1.0–1.8% Fe in 90/10; higher in C71640) is the critical design feature for flow resistance. Iron enters the protective film and dramatically increases its resistance to mechanical erosion by high-velocity seawater, sand, and entrained particles — the primary failure mode in seawater pumping systems.
Cu-Ni 90/10 and 70/30 are readily welded with ERCuNi (AWS A5.7) filler wire by GTAW, GMAW, or SMAW processes without preheat. Welds maintain the same seawater corrosion resistance as the base metal — a critical requirement for marine piping systems where weld zones are often the first point of attack in lesser alloys.
Properly designed Cu-Ni seawater piping systems routinely achieve 30–50 year service lives with no coating, no cathodic protection, and no chemical injection. The total life-cycle cost is far lower than carbon steel (which requires painting, CP, and periodic replacement) or even titanium (higher initial cost).
Cu-Ni 90/10 has a thermal conductivity of ~50 W/m·K — significantly higher than austenitic stainless steel (~15 W/m·K). This makes it particularly effective for heat exchanger shell connections, condenser water boxes, and seawater cooling system headers where heat transfer efficiency matters.
| Parameter | Cu-Ni 90/10 (C70600) | Cu-Ni 70/30 (C71500) | Titanium Gr. 2 | SS 316L |
|---|---|---|---|---|
| Seawater Corrosion | Excellent | Excellent + | Outstanding | Good (risk of crevice/pitting) |
| Biofouling Resistance | Excellent (natural) | Excellent (natural) | Poor | Poor |
| Erosion-Corrosion | Good (to ~1.5 m/s) | Very Good (to ~3.5 m/s) | Outstanding | Moderate |
| Tensile Strength | ~275 MPa | ~380 MPa | ~345 MPa | ~515 MPa |
| Max Service Temp | ~232°C | ~260°C | ~315°C | ~450°C |
| Weldability | Excellent | Excellent | Requires inert gas chamber | Good |
| Relative Material Cost | Moderate | Moderate-High | Very High | Moderate |
| Stress Corrosion Cracking | Immune in seawater | Immune in seawater | Immune | Risk in warm chloride-rich seawater |
| Primary Use Case | General marine seawater piping | High-velocity seawater, naval | Aggressive brine, high-temp saline | Chemical process, non-chloride service |
| Flange Type | Marine / Seawater Application Notes | Standard |
|---|---|---|
| Weld Neck (WNRF) | Preferred for high-pressure seawater headers, firewater mains, and pump discharge lines. Smooth bore transition minimises turbulence and erosion-corrosion at the flange bore. | ASME B16.5 / B16.47 |
| Slip-On (SORF) | Seawater cooling system headers, ballast piping, and non-critical utility connections. Double fillet weld. More economical than weld neck for moderate-pressure service. | ASME B16.5 |
| Blind Flange | End closures on seawater systems for maintenance, expansion ports on cooling headers, and isolation of vessel nozzles during dry-docking. | ASME B16.5 / B16.47 |
| Socket Weld (SWRF) | Small-bore seawater instrument connections, chemical injection lines, and instrument take-offs (NPS ½″–2″). Single fillet weld; no crevice concerns in low-flow service. | ASME B16.5 |
| Lap Joint (LJRF) | Used with Cu-Ni stub ends for systems requiring frequent dismantling — common at heat exchanger water box connections in marine power plants and desalination units. | ASME B16.5 |
| Threaded Flange | Low-pressure seawater utility connections where no welding is possible or practical. Sealant recommended to prevent crevice corrosion at thread roots. | ASME B16.5 |
| Long Weld Neck (LWN) | Nozzle connections on Cu-Ni-lined vessels, seawater heat exchanger shells, and desalination plant pressure vessels where a single forging provides both nozzle and flange. | ASME B16.5 / MSS SP-44 |
| Spectacle Blind / Spade | Positive isolation of seawater sections during vessel dry-docking, overhaul, and maintenance. Essential for offshore platforms during intervention operations. | ASME B16.48 |
| Material Standard | ASTM B564 / ASME SB564 — UNS C70600 (90/10), C71500 (70/30), C71640 |
| Size Range | ½″ NB to 24″ NB (DN 15 to DN 600) — larger sizes on request |
| Pressure Classes (ASME B16.5) | Class 150, 300, 600, 900, 1500, 2500 |
| Large Diameter (ASME B16.47) | Class 75, 150, 300, 400, 600, 900 — Series A & B |
| Dimensional Standards | ASME B16.5, ASME B16.47, MSS SP-44, EN 1092-1, DIN 2631–2638, BS 4504 |
| Facing Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G) |
| Testing & Inspection | Chemical analysis, tensile testing, hardness, PMI (XRF), dimensional inspection (100%), visual per MSS SP-55 |
| Material Certification | EN 10204 Type 3.1 (standard) / Type 3.2 (third-party witnessed) |
| Third-Party Inspection | Bureau Veritas, Lloyds Register, TÜVR, SGS, Intertek — on request |
| Welding Filler (GTAW/GMAW) | ERCuNi (AWS A5.7 / SFA 5.7) |
| Welding Electrode (SMAW) | ECuNi coated electrode |
| Client Specifications | Shell DEP, Norsok M-630, Lloyd's Register Type Approval, Naval MIL-SPEC |
| Grade | UNS Number | Alternate Designations | Sub-Page |
|---|---|---|---|
| Cupro Nickel 90/10 | C70600 | CuNi10Fe1Mn (EN), CN 102 (BS), 2.0872 (DIN) | 90/10 Flanges → |
| Cupro Nickel 70/30 | C71500 | CuNi30Mn1Fe (EN), CN 107 (BS), 2.0882 (DIN) | 70/30 Flanges → |
| Cu-Ni High-Iron | C71640 | CuNi30Fe2Mn2 (EN), 2.0883 (DIN) | C71640 Flanges → |
| Industry / Sector | Typical Cupro Nickel Flange Applications |
|---|---|
| Marine & Naval Vessels | Seawater cooling systems, fire main piping, bilge and ballast systems, hull fittings, seawater service headers on cargo vessels, tankers, and naval warships |
| Offshore Oil & Gas Platforms | Seawater lift pump discharge piping, firewater mains, seawater injection headers, cooling water systems, produced water treatment connections, deluge systems |
| Desalination Plants | Seawater intake and distribution headers, brine recirculation piping, multi-stage flash (MSF) heat exchanger connections, SWRO pre-treatment systems |
| Coastal & Marine Power Plants | Seawater-cooled steam condenser connections, cooling water intake and outfall headers, heat exchanger water box nozzles, circulating water pump flanges |
| Shipbuilding | All seawater service piping systems — cooling, firefighting, ballast, bilge, hull penetrations, sea chest connections, and salt water ballast valves |
| LNG & FPSO Vessels | Seawater cooling for LNG reliquefaction units, firewater mains, hull-integrated cooling systems, seawater service pumps on floating production vessels |
| Marine Aquaculture | Seawater intake and distribution piping for fish farms, shellfish hatcheries, and marine research facilities where biofouling control is critical |
| Process | Filler / Electrode | Key Requirements |
|---|---|---|
| GTAW / TIG | ERCuNi (AWS A5.7) | Argon back-purge on root pass; keep interpass temp ≤150°C; no preheat required |
| GMAW / MIG | ERCuNi (AWS A5.7) | Argon or Ar/He shielding gas; spray transfer preferred; clean joint surfaces essential |
| SMAW / Stick | ECuNi (coated electrode) | Dry electrodes (stored at 60–70°C); short arc; avoid weaving; chip slag between passes |
| Critical Precautions |
1. Joint must be absolutely free of oil, grease, paint, and moisture — any contamination causes porosity or hot cracking. 2. Sulfur is highly detrimental — do not weld near sulfur-containing materials or use sulfur-bearing marking pens on Cu-Ni. 3. Do not use carbon steel brushes or grinding discs on Cu-Ni surfaces — iron contamination promotes pitting. |
|
| Test / Inspection | Standard / Method | Frequency |
|---|---|---|
| Chemical Analysis | ASTM E1251 / OES Spectroscopy | Per heat |
| Tensile Testing | ASTM E8 / ASTM B564 | Per lot |
| Hardness Testing | ASTM E18 / E10 | Per piece (if required) |
| Positive Material Identification (PMI) | XRF / OES — confirms Ni, Cu, Fe content | Per piece (if required) |
| Dimensional Inspection | ASME B16.5 / B16.47 | 100% per piece |
| Visual Inspection | MSS SP-55 | 100% per piece |
| Hydrostatic / Pressure Test | ASME B16.5 / API 598 | As specified |
| Radiographic Testing (RT) | ASME Section V Art. 2 | As specified |
Cu-Ni 90/10 (C70600), 70/30 (C71500), C71640 — all types, all sizes, ASTM B564 & ASME SB564. Ready stock for immediate export to 65+ countries.