Seawater is the test that eliminates most fin tube materials. Copper-nickel passes it three ways at once: the alloy resists general seawater corrosion, it tolerates flow velocities that erode plain copper and brass, and the trace copper ions it releases keep marine growth from settling on the tube in the first place. USA Piping Solution supplies cupro-nickel fin tubes in 90/10 (C70600) and 70/30 (C71500), typically integral low fin to ASTM B111 and B359, for condensers, desalination plants, and offshore coolers. The full fin tube range across all base metals is mapped on our Finned Tubes page. For fresh or lightly brackish cooling water, our Admiralty Brass Fin Tube page covers the lower-cost option.
The Cooling Water Ladder
Condenser tube selection is mostly a question of how hard the water is working:
| Cooling Water | Alloy | Why |
|---|---|---|
| Fresh, clean, moderate velocity | Admiralty brass C44300 | Lowest cost of the inhibited copper alloys; the century-old default |
| Brackish or seawater, standard velocity | Cupro-nickel 90/10 (C70600) | Genuine seawater corrosion resistance plus biofouling resistance from copper ion release |
| Seawater at higher velocity or temperature, polluted or sulphide-bearing water | Cupro-nickel 70/30 (C71500) | More nickel raises velocity tolerance and resistance to polluted and warmer water |
| Extreme velocity or chemistry beyond copper alloys | Titanium or super-austenitic | Outside the copper-alloy family entirely |
Bare cupro-nickel tube in the same alloys is on our Copper Nickel 90/10 Pipes & Tubes page; this page covers the finned form, where integral low fins roughly triple the outside area without changing the tube sheet.
Why Fins Change the Economics
Copper-nickel is not a cheap alloy, which is exactly why finning it pays. Integral low fin is rolled from the tube's own wall, so there is no joint, no dissimilar metal, and no loss of the corrosion resistance the alloy was bought for. Roughly two and a half to three times the bare surface comes out of the same tube sheet layout and the same bundle envelope, so a retube can lift duty without touching the shell. In new build, the same logic runs the other way: fewer, shorter tubes for the same duty, and less expensive alloy in the machine.
Specifications
| Alloys | 90/10 cupro-nickel (C70600) · 70/30 cupro-nickel (C71500) |
| Standards | ASTM B111 / ASME SB111 (condenser and heat exchanger tube) · ASTM B359 (integral low-fin tube) |
| Construction | Integral low fin rolled from the tube wall; bare tube also available |
| Typical OD | 15.9 – 31.8 mm (5/8" – 1-1/4") condenser sizes |
| Fin Geometry | Low fin, typically 19 – 26 fins per inch, to design |
| Temper | Annealed (O61) standard for condenser service |
Applications
- Seawater-Cooled Condensers: power and process condensers on coastal and offshore intakes. See Condenser Tubes for the wider range.
- Desalination Plants: MSF and MED evaporator and heat-reject bundles.
- Offshore Platform Coolers: seawater-cooled utility and process coolers.
- Marine HVAC & Oil Coolers: shipboard chillers and lube oil coolers on raw water.
Retubing on Seawater? Send the Bundle Spec →
Testing, Certification & Availability
Tube ships to ASTM B111 or B359 with mill certification, eddy-current and hydrostatic testing per the standard, and full heat traceability; our Quality Policy page covers the program. Send alloy, OD, wall gauge, fin count, length, and quantity for availability and lead time.
Related Products
- Finned Tubes (all types)
- Admiralty Brass Fin Tube
- Copper Finned Tubes
- Copper Nickel 90/10 Pipes & Tubes
- Condenser Tubes
- Heat Exchanger Tubes & Pipes
Frequently Asked Questions
90/10 or 70/30 cupro-nickel for a seawater condenser?
90/10 (C70600) handles most seawater condenser duty and costs less. Step to 70/30 (C71500) when water velocity runs high, the water is warm, or the intake carries sulphides and pollution, all conditions where the extra nickel earns its price.
Does the fin reduce the alloy's seawater corrosion resistance?
No, because integral low fin is formed from the tube's own wall rather than attached. There is no joint, no crevice, and no second metal; the fin is the same alloy as the tube and behaves the same way in the water.
Is cupro-nickel resistant to marine biofouling?
Yes, and it is one of the alloy's practical advantages. Slow copper ion release discourages marine growth from settling, which keeps the tube transferring heat between cleanings, something stainless and titanium do not do on their own.
Can cupro-nickel fin tube be used in ammonia service?
No. Copper alloys, cupro-nickel included, are attacked by ammonia and ammonium compounds. Specify stainless or steel where ammonia contacts the tube.