Most copper alloys corrode in seawater. Some last a few years. Others fail within months. C70600 is different because of its chemistry. The nickel and iron work together to form a thin, protective layer on the tube surface. Once that layer forms (usually within days of seawater exposure), the tube is protected. The layer self‑repairs if scratched. No other common copper alloy does this as well. That is why engineers specify C70600 for critical seawater systems, not cheaper alternatives.
What is the exact chemical composition of C70600 per ASTM B111?
C70600 must contain 9.0-11.0% nickel, 1.0-1.8% iron, and no more than 1.0% manganese. Copper makes up the rest, with strict limits on lead, zinc, carbon, and phosphorus.
| Element | Min (%) | Max (%) | Typical (%) | Why it is there |
|---|---|---|---|---|
| Copper (Cu) | 86.5 (approx) | Remainder | ~87.5 | Base metal |
| Nickel (Ni) | 9.0 | 11.0 | 10.0-10.5 | Corrosion resistance |
| Iron (Fe) | 1.0 | 1.8 | 1.2-1.5 | Film formation |
| Manganese (Mn) | 0 | 1.0 | 0.5-0.8 | Deoxidizer |
| Lead (Pb) | 0 | 0.02 | <0.01 | Impurity |
| Zinc (Zn) | 0 | 0.5 | <0.1 | Impurity |
| Carbon (C) | 0 | 0.05 | <0.03 | Impurity |
| Phosphorus (P) | 0 | 0.02 | <0.01 | Impurity |
Where is C70600 tube most commonly used in the field?
Shipbuilding
Seawater cooling lines
Ballast water systems
Fire fighting mains
Bilge and stripping lines
Power plants (coastal)
Main condensers
Auxiliary coolers
Pump seal coolers
Turbine gland condensers
Desalination plants
Low temperature evaporators
Preheater tubes
Ejector condensers
Offshore platforms
Topside seawater piping
Fire water ring mains
Hydraulic control lines
Instrument air coolers
What are the practical advantages of using C70600 over other materials?
Advantage 1 – Long life
20-30 years in properly designed seawater systems
Compare to aluminum brass (5-10 years) or copper (1-2 years)
Less frequent retubing means lower lifecycle cost
Advantage 2 – Low maintenance
Copper ions prevent barnacle and mussel attachment
No internal cleaning required for biofouling
Oxide film is stable, no scaling issues
Advantage 3 – Predictable performance
Corrosion rate is uniform, not localized
No sudden pinhole leaks if designed correctly
Easy to inspect with eddy current
C70600 is not the cheapest tube upfront. But it is one of the cheapest over 30 years because you do not replace it every 5 years.
How does C70600 compare to C71500 for seawater service?
C70600 (90/10) is for normal seawater conditions. C71500 (70/30) is for higher velocity or higher temperature. Here is a side‑by‑side comparison.
| Factor | C70600 (90/10) | C71500 (70/30) |
|---|---|---|
| Nickel content | 9-11% | 29-33% |
| Max seawater velocity | 2.5-3.0 m/s | 4.0-4.5 m/s |
| Max temperature | 60°C | 80°C |
| Relative cost | 1.0x (baseline) | 1.3-1.5x |
| Weldability | Easier | Requires preheat |
| Thermal conductivity | 45 W/m·K | 40 W/m·K |
| Best application | Standard marine piping | High speed condensers |
When to pick which：
Normal seawater, under 2.5 m/s, under 60°C → C70600
Fast seawater, over 2.5 m/s, or hot seawater over 60°C → C71500
FAQ
Q1： What is the minimum nickel content for a tube to be called C70600?
9.0% is the absolute minimum per ASTM B111. Below 9.0%, it is not C70600. Some suppliers may try to sell material with 8.5% nickel as "C70600 type". Reject it. The nickel is what gives C70600 its corrosion resistance. Pay for the full spec.
Q2： Can I test the chemistry of C70600 tube myself?
Not without lab equipment. But you can hire an independent lab. Send a 50mm sample to a lab that does OES spectrometry per ASTM E1473. Cost is $100-200. Results in 3-5 days. Test for Ni, Fe, Mn, Pb, Zn. If results are out of spec, reject the batch.
Q3： Is C70600 the same as CuNi10Fe1Mn?
Yes, the numbers tell you： CuNi10 = 10% nickel. Fe1 = 1% iron. Mn = manganese. CuNi10Fe1Mn is the European (EN) designation. C70600 is the U.S. (UNS) designation. The chemistry ranges are equivalent. If you are exporting to Europe, use both names on your PO.
Q4： How long does C70600 tube last in a seawater cooled heat exchanger?
20-30 years is typical for properly designed systems. Factors that reduce life： velocity above 2.5 m/s, temperature above 60°C, sand or debris in water, sulfide pollution. In clean seawater at 1.5-2.0 m/s and 30-40°C, 30 years is realistic.
Q5： Can I weld C70600 to carbon steel?
Yes, but use ERCuNi filler metal and expect galvanic corrosion if the joint is immersed in seawater. For above‑water joints, welding is fine. For below‑water or wet service, isolate the two metals with a spool piece of C70600 or use a coated flange.
Q6： Does C70600 cost more than 316L stainless steel?
Yes, C70600 is usually 20-40% more expensive than 316L on a per‑kg basis. But in seawater, 316L pits and fails. C70600 lasts 5-10x longer. The lifecycle cost of C70600 is lower even though the upfront cost is higher.
Q7： What is the maximum flow velocity for C70600 tube in seawater?
2.5 m/s is the recommended maximum for continuous service. 3.0 m/s is acceptable for intermittent service. Above 3.0 m/s, impingement corrosion starts at tube inlets. If your system runs at 3.5-4.0 m/s, upgrade to C71500.
Q8： Can C70600 be used for drinking water on ships?
Yes, C70600 is approved for potable water systems on most vessels. The copper ions released are within safe limits. However, some water authorities require testing to confirm levels stay below local limits. For long term storage (stagnant water), flush before drinking.
Q9： How do I read the chemistry section of a Mill Test Report?
Look for the "heat analysis" section. It will list each element and the measured value. Check Ni between 9.0-11.0%. Check Fe between 1.0-1.8%. Check Pb under 0.02%. Check Zn under 0.5%. If any of these are out of range, reject the material.
Q10： Is C70600 magnetic?
No, C70600 is non‑magnetic. It contains only 9-11% nickel, well below the level (around 30%) where copper nickel becomes magnetic. This is important for applications near compasses or sensitive electronics.
Q11： What is the thermal conductivity of C70600?
45 W/m·K at 20°C. This is about 12% of pure copper (385 W/m·K) but 3 times higher than 316L stainless steel (15 W/m·K). For heat exchanger design, you need more surface area than pure copper but less than stainless steel.
Q12： Does ASTM B111 allow welded C70600 tube or only seamless?
ASTM B111 covers both seamless and welded tubes. However, seamless is by far the most common for C70600. Welded C70600 tube is rare and usually requires agreement between buyer and mill. If you receive welded tube without asking for it, reject it.
Our Testing
Chemistry (spectrometer, ASTM E1473) → Ni 9-11%, Fe 1.0-1.8%
Tensile (pull to break, ASTM E8) → 310 MPa minimum
Flatten (squeeze ring to 3x wall, ASTM B968) → no cracks
Flare (30° cone expansion, ASTM B969) → no splits
Eddy current (100% of tubes, ASTM E243) → reject any signal
What you get
Mill Test Report (MTR) with every order
Traceable by heat number
Third party inspection available (SGS, BV, Lloyds)
Our Packaging
tube
Plastic cap on both ends
VCI paper inside (upon request)
bundle
Shrink wrapped (seals out moisture)
Steel strapped (4-6 straps)
Wooden case for fragile sizes
Pallet + steel for standard 6m
label
Grade (C70600 / 90/10)
Size (OD x BWG)
Heat number (traceable)
Quantity and length
Our Factory Equipment
| Station | Equipment | What we make |
|---|---|---|
| 1 | Melting furnace (3x, 5 tons) | Liquid copper nickel alloy |
| 2 | Continuous caster (2 lines) | Solid billet 80-220mm |
| 3 | Extrusion press (2500T & 3500T) | Hollow tube shell |
| 4 | Pilger mill (4 units) | Reduced diameter |
| 5 | Drawing bench (8 lines) | Final OD and wall |
| 6 | Annealing furnace (4 units, 600°C) | Soft, bendable tube |
| 7 | Straightener & cutter (3 lines) | Straight, cut to length |
| 8 | Eddy current tester (2 machines) | 100% inspection |
Our Product Range
| Category | Shapes | Sizes | Grades |
|---|---|---|---|
| Tube | Round, square, coil, grooved | OD 3-219mm | C11000, C12200, C70600, C71500, C26000 |
| Rod | Round, hex, square | Dia 2-120mm | C11000, C36000, C14500, C18200 |
| Wire | Round, flat, tinned | Dia 0.1-12mm | C11000, C16200, C17200 |
| Strip | Coiled, slit | Thk 0.05-3mm | C11000, C19400, C70250 |
| Foil | Thin sheet | Thk 0.01-0.1mm | C11000, C10200 |
| CNC parts | Bushings, flanges, nuts | Custom | C36000, C63000, C70600 |
Discuss Your Project Requirements
