UNS C70600 (90/10 copper-nickel) is the most widely used copper-nickel alloy for seawater handling service. It contains nominally 10% nickel with iron additions (1.0-1.8%) which are necessary to maintain good corrosion resistance.
Copper-nickel alloys have high resistance to seawater environments and excellent inherent resistance to biofouling. C70600 is an established piping alloy for many of the world's navies, merchant shipping, power industry, and offshore platforms.
What is the Chemical Composition of C70600?
| Element | C70600 (90-10) |
|---|---|
| Copper (Cu) | ~89% (remaining) |
| Nickel (Ni) | 9.0 – 11.0% |
| Iron (Fe) | 1.0 – 1.8% |
| Lead (Pb) | <0.05% |
What are the Mechanical Properties of C70600 Tube (ASTM B111)?
| Temper | Code | 0.5% Proof Stress (MPa) | Tensile Strength (MPa) | Elongation (%) |
|---|---|---|---|---|
| Annealed | O61 | 105 | 275 (min) | 40 |
| Cold Drawn | H55 | 240 | 310 (min) | 10 |
What are the Physical Properties of C70600?
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.94 g/cm³ (at 20°C) | 0.323 lb/in³ (at 68°F) |
| Melting Point (Liquidus) | 1150°C | 2100°F |
| Melting Point (Solidus) | 1100°C | 2010°F |
| Thermal Conductivity | 40 W/m·K (at 20°C) | 23 BTU/ft³/ft/hr/°F (at 68°F) |
| Coefficient of Thermal Expansion | 17.1 x 10⁻⁶ /°C (20-300°C) | 9.5 x 10⁻⁶ /°F (68-392°F) |
| Modulus of Elasticity (Tension) | 140 GPa | 20 x 10⁶ psi |
| Modulus of Rigidity (Torsion) | 52 GPa | 7.5 x 10⁶ psi |
| Electrical Conductivity (Annealed) | 5.26 microhm⁻¹·cm⁻¹ | 9.1% IACS |
What is the Corrosion Resistance of C70600?
Key corrosion properties of C70600:
Low general corrosion rates: 0.0025-0.025 mm/year in seawater
Resistance to stress corrosion cracking: Highest resistance to ammonia stress corrosion; stress corrosion in seawater is not known to be a problem
High resistance to crevice corrosion & chloride stress corrosion: Not susceptible to the type of crevice corrosion found in stainless steels
Good pitting resistance: Pits tend to be broad and shallow rather than undercut
What are the Fabrication Properties of C70600?
| Joining Technique | Suitability |
|---|---|
| Soldering | Excellent |
| Brazing | Good |
| Gas Shielded Arc Welding | Excellent |
| Coated Metal Arc Welding | Good |
| Resistance Welding | Good |
| Oxy Acetylene Welding | Not Recommended |
| Fabrication Technique | Suitability |
|---|---|
| Cold Working | Excellent |
| Hot Working | Good |
| Machinability Rating | 20% (of free cutting brass) |
| Polishing/Electroplating Finish | Excellent |
Heat treatment temperatures:
Hot Working Temperature: 850 – 950°C
Annealing Temperature: 700 – 825°C
Stress Relieving Temperature: 275 – 400°C
What are the Applications of C70600?
| Application Area | Specific Uses |
|---|---|
| Seawater pipe work | Naval, merchant shipping, power industry, offshore platforms |
| Offshore fire water systems | Seawater deluge fire extinguishing systems |
| Heat exchangers & condensers | Where high reliability is required |
| Seawater intakes | Intake screens – high resistance to macrofouling |
| Fish farming | Underwater pens and enclosures – biocidal properties prevent fouling |
| Sheathing of legs & risers | Splash zone corrosion protection on oil/gas platforms |
| Boat hulls | Without cathodic protection or antifouling paints |
| Hydraulic lines | Marine hydraulic and instrumentation systems |
| Desalination units | Multi-Stage Flash Desalination Units (Middle East) |
What are the ASTM Specifications for C70600?
| Standard | Title |
|---|---|
| ASTM B111 | Seamless condenser tubes & ferrule stock |
| ASTM B466 | Seamless copper-nickel pipe and tube |
| ASTM B467 | Welded copper-nickel pipe |
| ASTM B151 | Rod and bar |
| ASTM B171 | Plate & sheet for pressure vessels, condensers & heat exchangers |
| ASTM B122 | Plate, sheet, strip & rolled bar |
| ASTM B359 | Seamless tubes with integral fins |
| ASTM B469 | Seamless tubes for pressure applications |
| ASTM B543 | Welded heat exchanger tube |
| ASTM B552 | Seamless & welded tubes for water desalting |
| ASTM B608 | Welded pipe |
FAQ
Q1: What is the difference between C70600 (90/10) and C71500 (70/30) copper-nickel for seawater service?
A: C70600 (90/10) has better biofouling resistance and is more cost-effective. C71500 (70/30) has higher strength and better resistance to impingement attack at higher water velocities.
Q2: What is the maximum seawater velocity for C70600 pipe?
A: C70600 pipe can be designed for flow rates up to 3.5 m/s with a satisfactory safety factor. Local speeds may be higher at changes of direction.
Q3: Does C70600 copper-nickel require post-weld heat treatment?
A: No, C70600 requires no post-weld heat treatment. It is readily weldable by conventional welding techniques.
Q4: Is C70600 resistant to stress corrosion cracking from ammonia?
A: Yes, C70600 has the highest resistance to ammoniacal stress corrosion cracking. Stress corrosion in seawater is not known to be a problem for copper-nickel.
Q5: How long does it take for C70600 to form its protective film in seawater?
A: C70600 typically forms its protective corrosion-resistant surface film in six to eight weeks of initial immersion.
Q6: What is the fouling resistance rating of C70600 compared to other alloys?
A: On a scale of 0-100, C70600 rates 90-100 (Best), equal to copper. This is significantly better than stainless steel and titanium (rated 0).
Q7: Can C70600 be welded to steel?
A: Yes, C70600 can be welded to steel using appropriate welding techniques and filler metals.
Q8: What is the annealing temperature for C70600 tube?
A: C70600 tube is annealed at 700 – 825°C.
Q9: What is the corrosion rate of C70600 in clean seawater?
A: C70600 has a general corrosion rate of 0.0025-0.025 mm/year in clean seawater.
Q10: Is C70600 susceptible to crevice corrosion?
A: No, C70600 has good tolerance to crevice corrosion. Crevices can normally be tolerated in designs using this material.
Q11: What is the maximum operating temperature for C70600?
A: Per AS1210, the maximum metal temperature for C70600 is 300°C. Per AS4041, it is 325°C.
Q12: Can C70600 be used for desalination units?
A: Yes, C70600 is a prime condenser tubing material for the Heat Recovery Section of Multi-Stage Flash Desalination Units.
Q13: What filler metal is recommended for welding C70600?
A: For welding C70600, use AWS A5.7 ERCuNi filler metal.
Q14: Is C70600 suitable for boat hulls without paint?
A: Yes, C70600 is one of the few engineering materials with good inherent resistance to both corrosion and biofouling, making it suitable for boat hulls without antifouling paints.
Quality Inspection for C70600
GNEE inspects C70600 following ASTM standards:
Chemical composition – Spectrometer verification of Cu, Ni, Fe, Pb
Mechanical testing – Tensile, proof stress, elongation (ASTM B111)
Flattening & expansion tests – For tube products
Non-destructive testing – Eddy current (ASTM E243) or hydrostatic
Dimensional & visual inspection – OD, ID, wall, length, surface
Packaging for C70600 Tube
C70600 tube is packaged for export:
Plastic end caps on both ends
VCI paper wrap or rust-prevention oil
Hexagonal bundles with steel strapping
Woven polypropylene or PE film overwrap
Wooden crates or pallets (ISPM-15 compliant)
Clear labeling: Alloy, standard, dimensions, heat number
Bundle weight: 2000-2500 kg | Length: 1m – 12m
Factory Equipment
| Equipment | Purpose |
|---|---|
| Induction furnace (30T) | Melting and alloying |
| Horizontal caster | Hollow billet production |
| Extrusion press (2500T) | Tube shell forming |
| Cold drawing bench | Precision drawing |
| Bright annealing furnace | Heat treatment (no scaling) |
| Eddy current & hydrostatic testers | 100% NDT |
| Universal testing machine | Mechanical properties |
Product Range
GNEE supplies all copper and copper alloy products:
| Category | Typical Grades | Forms |
|---|---|---|
| Pure Copper | C10100, C10200, C11000, C12200 | Tube, pipe, bar, plate, sheet, wire, strip |
| Copper-Nickel | C70600, C71500, CuNi30Fe | Tube, pipe, bar, plate, sheet, fitting, flange |
| Brass | C26000, C36000, C37700, C44300, C46400, C48500, C68700 | Tube, bar, plate, sheet, strip |
| Phosphor Bronze | C51000, C52100, C52400, C54400 | Bar, plate, sheet, strip |
| Aluminum Bronze | C61400, C62300, C63000, C63200, C95400, C95500 | Bar, plate, tube, forging |
| Silicon Bronze | C65100, C65500, C66100 | Bar, tube, wire |
| Beryllium Copper | C17200, C17500 | Bar, rod, wire, strip |
| Tin/Leaded Bronze | C90300, C90500, C93200, C93700 | Cast bar, bearing stock |
| Nickel Silver | C74500, C75200, C75400, C77000 | Bar, plate, sheet, strip |
All forms: Seamless tube (2-219mm OD), pipe (1/8" – 12" NB), bar (2-300mm dia), plate (3-150mm thk), sheet, wire, strip, fittings, flanges, forgings, castings.
