C70600 vs C12200： Copper Nickel or Pure Copper for Heat Exchanger Tubes？

When you specify tubes for a heat exchanger or condenser, one of the first decisions is material. C12200 (phosphorus deoxidized copper) has been the standard for years. But more engineers are switching to ASTM B111 C70600 (90/10 copper nickel) . Is the upgrade worth the cost? Or is C12200 still good enough for your job?

C12200 is pure copper (99.9% Cu) with a small amount of phosphorus. C70600 is a copper nickel alloy containing 9-11% nickel and 1-1.8% iron. This is the fundamental difference. The nickel and iron in C70600 create a protective oxide layer that C12200 does not have.

C70600 is far superior in seawater. C12200 should not be used in seawater at all. C12200 pure copper suffers from pitting, impingement corrosion, and erosion in flowing seawater. C70600 forms a protective oxide layer that blocks further attack.

Corrosion comparison in seawater：

C12200 has higher thermal conductivity. But in seawater service, corrosion kills heat transfer faster than the material difference. C12200 pure copper conducts heat about 5-6 times better than C70600. However, once C12200 corrodes and builds up scale, its actual heat transfer drops below that of a clean C70600 tube.

Thermal conductivity comparison：

Why C70600 still wins for seawater：

C12200 corrodes and forms scale (reduces heat transfer)

C70600 stays clean and oxide-stable

Fouled C12200 tube performs worse than clean C70600

Maintenance cost to clean C12200 is high

C70600 costs more than C12200. But tube failure and replacement cost much more. Typical price difference： C70600 is roughly 30-50% more expensive than C12200 per kg. However, a C12200 tube failure in a condenser means shutdown, labor, and lost production.

Cost comparison：

C70600 costs more upfront but saves money over the life of the equipment. C12200 is false economy for seawater.

Use C12200 for fresh water, cooling towers, closed loops, and HVAC systems where water is treated. C12200 is still the right choice for many clean water applications. It has excellent thermal conductivity and is easy to fabricate.

Good applications for C12200：

Closed loop chilled water systems

Cooling tower circuits with inhibitors

Domestic water heating

HVAC evaporators and condensers (fresh water)

Process cooling with treated water

Refrigeration systems

Use C70600 anywhere the tube touches seawater, brackish water, or untreated river water with high chlorides. Also upgrade for polluted water, high velocity, or any marine environment.

Must‑upgrade applications for C70600：

Marine condensers (seawater cooled)

Shipboard heat exchangers

Offshore platform coolers

Desalination plant evaporators

Seawater intake strainers and coolers

Brackish water power plants

Any location where C12200 failed before

Buy C70600 for seawater or brackish water condensers. Buy C12200 only for fresh water or treated closed loops. Do not let upfront cost drive your decision. A C12200 tube that fails in 12 months will cost you downtime, labor, and replacement tubes. That single failure often exceeds the entire material savings.

Fresh water, treated loops → C12200 copper

Seawater, brackish water, high chlorides → C70600 copper nickel

Q1： What is the difference between C70600 and C12200?

C70600 is a copper nickel alloy with 9-11% nickel. C12200 is pure copper with a small amount of phosphorus. The nickel in C70600 makes it highly resistant to seawater corrosion. C12200 has no nickel and will pit and erode in seawater. For fresh water, both work, but C12200 has better heat transfer.

Q2： Which is more corrosion resistant C70600 or C12200?

C70600 is much more corrosion resistant, especially in seawater. C12200 pure copper cannot handle flowing seawater. It suffers from impingement corrosion, pitting, and erosion. C70600 forms a protective nickel‑iron oxide layer that blocks further attack. In fresh water, both perform well.

Q3： Does C12200 work in seawater?

Not for long. C12200 will fail within 6 to 18 months in flowing seawater. The combination of chlorides, oxygen, and flow velocity attacks pure copper rapidly. You will see pinhole leaks, erosion grooves, and eventually tube rupture. Never use C12200 for seawater heat exchangers or piping.

Q4： Which has higher thermal conductivity C70600 or C12200?

C12200 has higher thermal conductivity on paper. C12200 is about 385 W/m·K. C70600 is about 45 W/m·K. However, in real seawater service, C12200 corrodes and forms scale, which blocks heat transfer. A corroded C12200 tube performs worse than a clean C70600 tube.

Q5： Is C70600 worth the extra cost over C12200?

Yes for seawater. No for fresh water. In seawater, a C12200 tube may fail in one year. Shutdown, labor, and replacement will cost far more than the material savings. C70600 lasts 20-30 years. For fresh water, C12200 is fine and cheaper. For seawater, C70600 pays for itself many times over.

Q6： Can I replace C12200 with C70600 without redesigning my heat exchanger?

Usually yes, but check two things. First, C70600 has lower thermal conductivity, so you may need slightly more surface area. Second, the tube OD is the same, so tube sheet holes do not need re‑drilling. Most engineers simply swap C12200 for C70600 in seawater service without major redesign.

Q7： Which is easier to weld C70600 or C12200?

C12200 is slightly easier to weld because it is pure copper. However, both are weldable with TIG or MIG. C12200 requires higher heat input because copper conducts heat away quickly. C70600 is more forgiving because its lower thermal conductivity keeps heat in the weld zone. Both need proper shielding gas.

Q8： Does C12200 suffer from dezincification?

No. C12200 does not contain zinc, so dezincification is not an issue. Dezincification affects brass alloys like C26000 or C36000. C12200 is pure copper. It fails by pitting and erosion, not dezincification. C70600 also does not contain zinc, so dezincification is not a concern for either material.

Q9： Can I use C12200 for marine heat exchangers?

No. Do not use C12200 in any marine heat exchanger that touches raw seawater. It will fail quickly. Classification societies like ABS, DNV, and Lloyds do not approve C12200 for seawater‑cooled heat exchangers. They require copper nickel (C70600 or C71500) or other approved alloys.

Q10： Which one do power plants use for condensers?

Power plants use C70600 or C71500 for seawater‑cooled condensers. For fresh water‑cooled plants, they may use C12200 or stainless steel. In coastal power plants with once‑through seawater cooling, copper nickel is the standard. C12200 is rarely seen in seawater condensers because failure risk is too high.

Q11： How long does C12200 last in seawater compared to C70600?

C12200： 6 to 18 months. C70600： 20 to 30 years. This is the real difference. A C12200 tube may survive one season in seawater. C70600 will outlast the equipment. If your condenser is critical, the choice is obvious. Do not gamble with pure copper in salt water.

Q12： Does C70600 have any disadvantage compared to C12200?

Two disadvantages： higher upfront cost and lower thermal conductivity. But in seawater, these are minor compared to C12200's corrosion failure. The lower thermal conductivity can be offset by adding a few more tubes or slightly increasing tube length. The higher cost is recovered in the first few years of trouble‑free operation.

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