Hangbo Alloy Group
Shanghai · Est. 2012
UNS C70600 / W.Nr. 2.0872 — The world's most widely used cupronickel for seawater service. Outstanding corrosion resistance, natural biofouling resistance, and excellent thermal conductivity for marine condensers, heat exchangers, and piping systems.
Copper-Nickel 90/10 (UNS C70600 / W.Nr. 2.0872) is the most widely used copper alloy in marine engineering worldwide. Its dominance in seawater-cooled heat exchangers, power plant condensers, and marine piping systems is no accident — it results from a unique combination of properties that no other alloy can match at its price point.
The alloy contains approximately 90% copper and 10% nickel, with critical additions of 1.0–2.0% iron and 0.5–1.0% manganese. The iron addition is not incidental — it is the single most important alloying element after nickel itself. Without iron, the alloy would have significantly poorer impingement corrosion resistance and would be unsuitable for most practical seawater applications. The iron enriches the protective surface film, creating an adherent, self-healing barrier that withstands flowing seawater velocities up to 2.5–3.0 m/s.
What sets C70600 apart from other seawater-resistant alloys (such as titanium, super duplex stainless steels, or nickel-based alloys) is its natural biofouling resistance. The controlled release of copper ions at the surface inhibits the settlement and growth of marine organisms — barnacles, algae, mussels, and bacteria — without any chemical antifouling coating. This eliminates a major maintenance cost and environmental concern in marine systems. Combined with excellent thermal conductivity (50 W/(m·K), roughly 2.5× that of stainless steel), C70600 is the default choice for seawater heat exchanger tubing globally.
Hangbo Alloy Group supplies C70600 in seamless tubes, welded pipes, plates, bars, fittings, and forgings — all with EN 10204 3.1 mill test certificates and marine classification approvals. Stock available for immediate delivery.
The chemical composition of Copper-Nickel 90/10 is carefully controlled to optimize seawater corrosion resistance. The table below presents the composition per ASTM B122/B466/B111 specifications.
| Element | Weight % (Range) | Typical % | Role in the Alloy |
|---|---|---|---|
| Copper (Cu) | Balance | ~88.0 | Base matrix, biocidal surface activity, high thermal conductivity |
| Nickel (Ni) | 9.0 – 11.0 | 10.0 | Corrosion resistance enhancement, solid solution strengthening, film stability |
| Iron (Fe) | 1.0 – 2.0 | 1.5 | Critical addition: enriches protective film, impingement & erosion corrosion resistance |
| Manganese (Mn) | 0.5 – 1.0 | 0.7 | Deoxidation, hot workability improvement, sulfur fixation |
| Carbon (C) | ≤ 0.05 | ~0.02 | Low carbon prevents grain boundary carbide precipitation |
| Lead (Pb) | ≤ 0.03 | ~0.005 | Controlled to prevent hot shortness and weld cracking |
| Sulfur (S) | ≤ 0.02 | ~0.005 | Impurity control for weldability and hot workability |
| Phosphorus (P) | ≤ 0.02 | ~0.005 | Impurity control |
| Zinc (Zn) | ≤ 1.0 | ~0.1 | Controlled to maintain corrosion resistance |
| Tin (Sn) | ≤ 0.03 | ~0.01 | Impurity control |
Key compositional insight: The 1.0–2.0% iron content is what separates C70600 from a simple Cu-10Ni binary alloy. Iron partitions to the protective oxide film, forming iron-rich oxyhydroxide (FeOOH) layers that dramatically improve resistance to flowing seawater. Without this iron addition, the alloy's critical velocity (the seawater flow rate at which impingement corrosion begins) would be only about 1.5 m/s instead of the 2.5–3.0 m/s achieved by C70600.
| Property | Value | Units |
|---|---|---|
| Density | 8.94 | g/cm³ |
| Melting Range | 1100 – 1145 | °C |
| Melting Range | 2010 – 2093 | °F |
| Thermal Expansion Coefficient (20–100°C) | 17.0 × 10−6 | /°C |
| Thermal Expansion Coefficient (20–300°C) | 17.8 × 10−6 | /°C |
| Thermal Conductivity (at 20°C) | 50 | W/(m·K) |
| Thermal Conductivity (at 200°C) | 52 | W/(m·K) |
| Specific Heat Capacity (at 20°C) | 377 | J/(kg·K) |
| Elastic Modulus (at 20°C) | 140 | GPa |
| Elastic Modulus (at 200°C) | 134 | GPa |
| Electrical Resistivity (at 20°C) | 0.19 | μΩ·m |
| Electrical Conductivity (IACS) | ~9 | % IACS |
| Poisson's Ratio | 0.34 | — |
| Crystal Structure | Face-Centered Cubic (FCC) — alpha phase | |
Thermal conductivity advantage: At 50 W/(m·K), C70600 has roughly 2.5 times the thermal conductivity of austenitic stainless steel (16 W/(m·K)) and over 5 times that of nickel-based alloys like Inconel 625 (9.8 W/(m·K)). This is a critical advantage in heat exchanger design — it means smaller, lighter, and less expensive heat exchangers can achieve the same thermal duty, or alternatively, existing heat exchanger designs can handle higher heat loads when retubed from stainless steel to C70600.
| Property | Annealed Condition | Cold-Drawn (Condenser Tube) | ASTM B466 Min. (Annealed) |
|---|---|---|---|
| Tensile Strength (Rm) | 275 – 380 MPa (40 – 55 ksi) | 350 – 450 MPa (51 – 65 ksi) | ≥ 275 MPa (40 ksi) |
| Yield Strength (Rp0.2) | 105 – 150 MPa (15 – 22 ksi) | 280 – 380 MPa (41 – 55 ksi) | ≥ 105 MPa (15 ksi) |
| Elongation (A) | 30 – 42% | 15 – 25% | ≥ 30% |
| Reduction of Area | 45 – 60% | 30 – 45% | — |
| Hardness | 65 – 90 HV | 100 – 140 HV | — |
| Impact Toughness (ISO-V, RT) | ≥ 180 J/cm² | — | — |
| Impact Toughness (ISO-V, −196°C) | ≥ 160 J/cm² | — | — |
C70600 retains moderate strength at elevated temperatures, though it is primarily used at temperatures below 200°C in pressure-containing applications. The following data illustrates typical property retention at temperature.
| Temperature (°C) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| Room Temperature | 320 | 120 | 38 |
| 100 | 290 | 108 | 35 |
| 200 | 260 | 95 | 32 |
| 300 | 220 | 85 | 30 |
C70600 exhibits good high-cycle fatigue performance in seawater environments. The fatigue limit at 10&sup8; cycles in seawater is approximately 120–140 MPa (annealed), which is notably maintained in the corrosive environment — unlike carbon steel which suffers significant corrosion fatigue reduction. At temperatures above 200°C, creep becomes a consideration for pressure-bearing components; ASME B31.3 limits the maximum allowable stress for C70600 at 200°C to 62 MPa.
The corrosion resistance of C70600 in seawater is achieved through a unique multi-layer protective film mechanism that develops naturally upon exposure to clean seawater. Understanding this mechanism is essential for proper application of the alloy.
When C70600 is first exposed to clean, aerated seawater, a thin protective film forms within hours to days. The film consists of multiple layers:
This film is self-healing: if mechanically damaged (e.g., by foreign object impingement), it reforms within hours in clean seawater. However, this healing requires aerated, flowing seawater — stagnant or polluted water conditions can prevent proper film formation.
In properly operating seawater systems, C70600 exhibits extremely low general corrosion rates:
The natural biofouling resistance of C70600 is one of its most valuable properties and a key reason it remains preferred over stainless steel or titanium in many marine applications. The mechanism:
This inherent biofouling resistance eliminates the need for chemical antifouling coatings, reduces maintenance frequency for cleaning, and minimizes environmental impact from biocide release. In power plant condensers, this translates to sustained heat transfer efficiency over years of operation without the performance degradation that affects stainless steel and titanium systems.
The maximum seawater velocity that C70600 can withstand without impingement corrosion is a critical design parameter:
| Application | Max Velocity (m/s) | Notes |
|---|---|---|
| Condenser tubes (continuous flow) | 2.5 – 3.0 | Standard design velocity: 1.8–2.4 m/s |
| Heat exchanger tubes | 2.0 – 2.5 | Conservative for long service life |
| Piping (straight sections) | 3.0 – 3.5 | Avoid turbulence at bends and inlets |
| Pump inlets/valve throats | 1.5 – 2.0 | High turbulence zones need lower velocity |
Copper-Nickel 90/10 has excellent weldability and is routinely fabricated into complex piping systems, heat exchangers, and pressure vessels.
The recommended filler metal for C70600 is Cu-30Ni (ERNiCu-7 type or ISO CuNi30Mn1Fe) — a 70/30 cupronickel composition. Using a 70/30 filler for 90/10 base metal is standard industry practice because:
Contact our technical sales team for pricing, availability, and metallurgical support. We supply C70600 globally with full certifications, marine approvals, and competitive mill-direct pricing.
The single largest application of C70600 is main condenser tubing in coastal and estuarine power stations (fossil fuel and nuclear). These condensers typically contain 10,000–30,000 tubes per unit, with tube lengths of 10–20 meters and OD of 19–32mm. C70600 has demonstrated service lives of 20–40+ years in properly maintained condensers, making it the benchmark material for this application. Key advantages over competing materials:
Hangbo Alloy Group supplies Copper-Nickel 90/10 in the following product forms, all manufactured to applicable ASTM/ASME specifications:
| Product Form | Applicable Standard | Typical Size Range |
|---|---|---|
| Seamless Condenser Tubes | ASTM B111 / ASME SB111 | OD 6 – 50mm, Wall 0.5 – 3.0mm |
| Seamless Pipes & Tubes | ASTM B466 / ASME SB466 | OD 6 – 300mm, Wall 1 – 15mm |
| Welded Pipes | ASTM B467 / ASME SB467 | OD 50 – 1200mm, Wall 2 – 20mm |
| Plates (Hot-Rolled) | ASTM B122 | Thickness 3.0 – 50mm |
| Sheets (Cold-Rolled) | ASTM B122 | Thickness 0.5 – 3.0mm |
| Strips / Coils | ASTM B122 | Thickness 0.1 – 2.0mm |
| Round Bars / Rods | ASTM B151 | Diameter 6 – 200mm |
| Butt-Weld Fittings | Custom / MSS-SP | Elbows, Tees, Reducers (1/2" – 24" NPS) |
| Forgings | Custom | Flanges, Tube Sheets, Custom Shapes |
All products are supplied with EN 10204 Type 3.1 material certificates including chemical analysis, mechanical test results, and NDT reports as applicable. Marine classification society approvals (DNV, ABS, LR, BV) available upon request.
| Standard | Description |
|---|---|
| ASTM B111 | Standard Specification for Copper and Copper-Alloy Seamless Condenser Tubes and Ferrule Stock |
| ASTM B466 | Standard Specification for Copper-Nickel-Zinc Alloy and Copper-Nickel Seamless Pipe and Tube |
| ASTM B467 | Standard Specification for Welded Copper-Nickel Pipe |
| ASTM B122 | Standard Specification for Copper-Nickel Alloy Plate, Sheet, Strip, and Bar |
| ASTM B151 | Standard Specification for Copper-Nickel-Zinc Alloy and Copper-Nickel Rod and Bar |
| ASTM B543 | Standard Specification for Welded Copper and Copper-Alloy Heat Exchanger Tube |
| ASME SB111/SB466/SB467 | ASME Boiler & Pressure Vessel Code equivalents |
| DIN/EN W.Nr. 2.0872 | German/European designation (CuNi10Fe1Mn) |
| ISO 426-1 | Wrought copper-nickel alloys — compositions and products |
| GB/T BFe10-1-1 | Chinese national standard equivalent grade |
| AWS A5.6 ECuNi | Covered electrode specification for SMAW |
| AWS A5.7 ERCuNi | Bare wire specification for GTAW/GMAW |
| DNV / ABS / LR / BV | Marine classification society type approvals |
| Property | Cu-Ni 90/10 (C70600) | Cu-Ni 70/30 (C71500) | Ti Gr.2 | 316L SS |
|---|---|---|---|---|
| Ni Content | 10% | 30% | 0% | 10% |
| Tensile Strength | 275–380 MPa | 370–450 MPa | 345–450 MPa | 480–620 MPa |
| Thermal Conductivity | 50 W/(m·K) | 29 W/(m·K) | 16 W/(m·K) | 16 W/(m·K) |
| Biofouling Resistance | Excellent | Good | Poor | Poor |
| Max Seawater Velocity | 2.5–3.0 m/s | 3.0–4.0 m/s | 5.0+ m/s | 1.5–2.0 m/s |
| Relative Cost | 1.0 (baseline) | 1.4–1.8 | 2.0–2.5 | 0.5–0.8 |
| Typical Service Life (condenser) | 20–30+ years | 25–40+ years | 30+ years | 5–10 years* |
*316L is generally not recommended for seawater service due to pitting and crevice corrosion; included for comparison only.
Selection guideline: For most seawater heat exchanger and piping applications at velocities ≤2.5 m/s, C70600 (90/10) is the most cost-effective choice. Upgrade to C71500 (70/30) for higher velocities, more severe service, or when longer service life justifies the premium. Consider titanium only when extreme velocity, pollution resistance, or very long design life (50+ years) is required.
Copper-Nickel 90/10 (UNS C70600) is a cupronickel alloy with 90% copper, 10% nickel, and critical additions of 1-2% iron and 0.5-1% manganese. It is the most widely used alloy for seawater-cooled heat exchangers and marine piping because of its excellent seawater corrosion resistance, natural biofouling resistance (no need for antifouling coatings), high thermal conductivity (50 W/(m·K)), and cost-effectiveness compared to titanium or nickel-based alloys.
Nominal composition (wt%): Cu balance (~88%), Ni 9.0-11.0%, Fe 1.0-2.0%, Mn 0.5-1.0%, C ≤0.05%, Pb ≤0.03%, S ≤0.02%, P ≤0.02%, Zn ≤1.0%. The 1-2% iron is critical — it enriches the protective surface film with iron oxyhydroxide (FeOOH), dramatically improving impingement corrosion resistance and enabling higher seawater flow velocities.
C70600 has a density of 8.94 g/cm³ (0.323 lb/in³) and a melting range of 1100-1145°C (2010-2093°F). Its thermal expansion coefficient from 20-100°C is 17.0 × 10−6 /°C, thermal conductivity at 20°C is 50 W/(m·K), and elastic modulus at 20°C is 140 GPa.
C70600 has a thermal conductivity of 50 W/(m·K) — roughly 2.5 times that of stainless steel (16 W/(m·K)) and 5 times that of Inconel 625 (9.8 W/(m·K)). In heat exchanger design, this means C70600 tubes can achieve the same heat transfer duty with smaller surface area, enabling more compact, lighter, and less expensive heat exchangers. This is a major reason C70600 remains preferred over titanium in many condenser applications despite titanium's superior corrosion resistance.
C70600 releases trace copper ions (Cu²+) at the surface, which are naturally biocidal to marine organisms at the settlement stage. This prevents barnacles, algae, mussels, and bacteria from adhering to the surface. The release rate is self-regulating — it decreases as the protective film matures. This inherent biofouling resistance eliminates the need for chemical antifouling coatings, reduces maintenance, and maintains heat transfer efficiency over years of service.
For condenser tubes, the recommended maximum continuous flow velocity is 2.5-3.0 m/s. Standard design velocity is 1.8-2.4 m/s for long service life. For piping in straight sections, 3.0-3.5 m/s is acceptable, but turbulence-prone areas (pump inlets, valve throats, bends) should be limited to 1.5-2.0 m/s. For higher velocity service, Copper-Nickel 70/30 (C71500) is recommended.
Yes, C70600 has excellent weldability using GTAW (TIG), GMAW (MIG), SMAW, and SAW processes. The recommended filler metal is Cu-30Ni (70/30 cupronickel composition) rather than matching 90/10 filler — the higher nickel compensates for dilution and provides better hot-cracking resistance. Pre-heating is generally not required for thin sections. No post-weld heat treatment is needed. Thorough cleaning before welding is essential to avoid sulfur contamination that can cause cracking.
C70600 (90/10) is less expensive and has higher thermal conductivity (50 vs 29 W/(m·K)) and better biofouling resistance. C71500 (70/30) offers higher strength, better erosion resistance at high velocities, and superior crevice corrosion resistance. For most seawater service at ≤2.5 m/s velocity, 90/10 is the cost-effective default. For higher velocity or more severe service, 70/30 is the upgrade choice.
The largest single application is power plant condenser tubing (coastal and nuclear stations). Other major uses include: marine heat exchangers and coolers, seawater piping for ships and offshore platforms, desalination plant tubing (MSF/MED), firewater systems, hydraulic/instrumentation tubing, boat hull sheathing, and aquaculture cage mesh. C70600 is also used for coinage in many countries.
Typical pricing: $12-22/kg for seamless condenser tubes, $10-18/kg for welded pipes, $14-26/kg for plates, $12-20/kg for bars. Pricing follows LME copper and nickel indices. Lead times: 4-8 weeks for custom mill production, 1-3 weeks for stock sizes. MOQ: 100 kg (tubes), 200 kg (plates). Contact serena@hangboalloy.com for a competitive quote with full certifications.
In properly designed and maintained systems, C70600 condenser tubes typically last 20-30+ years, with some installations exceeding 40 years. Factors affecting service life include water quality (pollution, H&sub2;S, ammonia), flow velocity, maintenance practices (sponge ball cleaning, deposit removal), and galvanic compatibility with connected materials. In clean seawater with proper design, the general corrosion rate is only 0.02-0.05 mm/year, meaning a 1mm wall thickness tube could theoretically last 20-50 years based on corrosion allowance alone.
Hangbo Alloy Group supplies C70600 in: seamless condenser tubes (ASTM B111, OD 6-50mm), seamless pipes/tubes (ASTM B466, OD 6-300mm), welded pipes (ASTM B467, OD 50-1200mm), plates/sheets/strips (ASTM B122, 0.5-50mm), round bars (ASTM B151, 6-200mm), butt-weld fittings, and custom forgings (flanges, tube sheets). All products come with EN 10204 3.1 certificates and marine classification approvals. Contact serena@hangboalloy.com or +86 166 2109 2936 (WhatsApp) for availability.
Shanghai Hangbo Alloy Group is a trusted global supplier of copper-nickel alloys and nickel-based superalloys with over 15 years of manufacturing expertise. We provide C70600 with full mill certifications, marine approvals, competitive pricing, and reliable delivery worldwide.