What ASTM B466 Covers
ASTM B466 is the standard specification for seamless copper-nickel pipe and tube in UNS C70600 (90/10 cupronickel) and UNS C71500 (70/30 cupronickel). It is published in parallel as ASME SB466, and both documents carry the same requirements, so material ordered to either designation is interchangeable for the same pressure and corrosion duty. Tube is produced by extrusion followed by cold drawing, and it is normally supplied in straight lengths in the annealed temper with plain, bevelled or threaded ends.
B466 is the reference document for seawater piping on ships, offshore installations, desalination plants and coastal power stations. The 90/10 composition combines useful strength with a level of chloride and erosion-corrosion resistance that neither carbon steel nor 300-series stainless steel can match in flowing seawater, which is why it has been the default choice for shipbuilding and ship repair work for decades.
Chemical Composition of UNS C70600
| Element | Requirement, % |
|---|---|
| Copper | Remainder, nominally 88.6 |
| Nickel | 9.0 - 11.0 |
| Iron | 1.0 - 1.8 |
| Manganese | 1.0 max |
| Zinc | 1.0 max |
| Lead | 0.05 max |
| Other elements, total | 0.5 max |
Iron is the element that controls resistance to impingement attack, so the 1.0 - 1.8 % window is deliberately narrow and is verified on every heat. Manganese supports hot workability, while the zinc and lead ceilings protect weld soundness and the integrity of expanded tube-to-tubesheet joints.
Mechanical and Physical Properties
| Property | Typical value |
|---|---|
| Density | 8.94 g/cm³ |
| Melting range | 1,100 - 1,140 °C |
| Thermal conductivity | about 45 W/(m·K) |
| Electrical conductivity | about 9 % IACS |
| Modulus of elasticity | about 150 GPa |
| Coefficient of thermal expansion | 17.1 um/(m.K), 20 - 300 °C |
Annealed C70600 tube is supplied with a minimum tensile strength of 275 MPa (40 ksi), a 0.5 % extension yield strength of about 105 MPa (15 ksi) and a minimum elongation of 30 % in 50 mm. The melting range of the 90/10 alloy lies between roughly 1,100 °C and 1,140 °C; figures above 1,400 °C that appear in some published tables describe unalloyed copper and do not apply to cupronickel.
Size Range, Condition and Test Requirements
| Item | Range |
|---|---|
| Outside diameter | 6 mm to 168 mm (1/4 in to 6 in) |
| Wall thickness | 0.8 mm to 12 mm |
| Straight lengths | Single random 5 - 7 m, double random 10 - 12 m, cut lengths to order |
| Standard temper | Annealed O61 |
| End finish | Plain, bevelled, threaded, grooved |
| Pressure and tightness tests | Hydrostatic and eddy current testing |
B466 tube is routinely subjected to tensile, flattening, expansion and eddy current examination, backed by dimensional checks and surface inspection. A mill test certificate to EN 10204 3.1 is issued with each shipment, and third-party inspection can be arranged for shipyard and classification society requirements.
Shipbuilding, Repair and Marine Applications
Seawater cooling, ballast and bilge piping on commercial and naval vessels.
Main and auxiliary condenser tubing, oil coolers and heat exchanger bundles.
Firemain, deckwash and sanitary seawater lines where galvanised steel fails quickly.
Fresh water generator and desalination evaporator tubing.
Ship repair and refit work, replacing corroded steel or aluminium-brass lines.
Offshore platform and FPSO seawater service piping and utility systems.
Circulating water and cooling systems in coastal power stations and industrial plants.
In seawater the alloy forms a thin, adherent oxide film that is continuously repaired by the dissolved iron in the matrix, and the copper ions released at the surface discourage the settlement of barnacles and other marine organisms. The material is not susceptible to chloride stress-corrosion cracking, and it retains useful toughness at low ambient temperatures.
Fabrication, Welding and Installation Notes
Copper-nickel is readily welded with matching filler metals: ERNiCu-7 for gas tungsten arc and gas metal arc welding, and ENiCu-7 covered electrodes for manual metal arc work. No preheat is required, heat input should be kept low, interpass temperature should stay below about 150 °C, and the joint area must be free of oil, paint and marking fluids before welding. Silver brazing and bronze welding are used for small bore connections and for repair work at sea.
Tube is normally expanded or roller-expanded into tubesheets; expansion is easier and more reliable than for steel tube, and no stress-relief treatment is needed afterwards. Where cupronickel meets carbon steel or a stainless steel in a seawater circuit, an insulating gasket or a transition spool should be used to break the galvanic couple, and sacrificial anodes are maintained on the steel side. Design velocities for clean seawater are usually held between 1.0 m/s and 3.0 m/s; below 1.0 m/s the risk of deposits and under-deposit corrosion rises, while excessive velocity combined with entrained sand causes impingement attack.
Quality Control Points for Buyers
Purchase orders should state the standard and grade, the temper, outside diameter and wall thickness, the length pattern, and whether eddy current testing or an additional hydrostatic test is required. Positive material identification, grain size checks and surface condition documentation are worth specifying for critical condenser work. Tube ends should be capped for transport, and material should be stored away from carbon steel offcuts to avoid iron contamination, which can trigger localised corrosion in service.
FAQ
Q: What is the difference between ASTM B466 and ASTM B111?
ASTM B111 covers seamless copper and copper-alloy tube for condensers and heat exchangers, while ASTM B466 is dedicated to copper-nickel pipe and tube in UNS C70600 and UNS C71500. Both are issued in matching ASME versions, so tubes specified to ASME SB111 and pipe specified to ASME SB466 are made to the same alloy chemistry.
Q: Why is 90/10 preferred over 70/30 cupronickel?
The 90/10 alloy is less expensive and has higher thermal conductivity, which suits most clean and moderately polluted seawater duties. The 70/30 grade is chosen where water velocity is high, where the water carries sand or suspended solids, or where the piping is exposed to severe turbulent flow.
Q: Can C70600 tube be welded in a shipyard repair?
Yes. The alloy is welded with copper-nickel filler metal using standard gas tungsten arc equipment. Cleanliness, low heat input and a controlled interpass temperature are the key points, and the weld should be pickled or brushed afterwards to restore the protective surface film.
Q: Is cupronickel suitable for stagnant seawater?
Cupronickel performs best with continuous flow. In lines that stand idle for long periods, deposits and sulphate-reducing bacteria can cause localised attack, so dead legs should be avoided and systems should be flushed before return to service.
Q: What documentation is supplied with a shipment?
Mill test certificates to EN 10204 3.1 covering chemical composition, mechanical properties and non-destructive test results are supplied as standard, together with dimensional inspection records and, where requested, third-party inspection certificates.
Q: What wall thickness should be selected for a seawater line?
Wall thickness is normally set by the design code and by a corrosion allowance rather than by pressure alone. Many marine specifications take a minimum wall of about 1.2 mm for small bore lines and thicker walls for large diameter seawater mains subject to erosion.
