Why Copper-Nickel Still Dominates Seawater and Brine Service

The 90/10 and 70/30 grades are copper-base alloys with 10 % or 30 % nickel, plus small but deliberate additions of iron and manganese. Those Fe and Mn additions are not incidental — they form a stable, self-healing surface film that gives the alloy its well-known resistance to flowing seawater, erosion–corrosion, pitting, stress-corrosion cracking and ammonia attack. In clean seawater, a 90/10 system typically shows a corrosion rate of 0.02 to 0.05 mm/yr and tolerates water velocities up to roughly 3.5–4.0 m/s; the higher-nickel 70/30 grade tolerates up to about 4.5 m/s, which is why it is preferred for high-velocity brine heaters and naval condensers.

A second, less-discussed advantage is biofouling economics. Cu-Ni's natural resistance to macrofouling means operators can often reduce or eliminate chlorination dosing and avoid anti-fouling coatings on pipe internals. Across a 25- to 30-year ship life, that single attribute can pay for the alloy premium several times over in reduced maintenance, fewer cleanings and longer intervals between dry-dockings.

90/10 vs 70/30: How to Choose Between the Two Workhorse Grades

For most marine and offshore piping, 90/10 (UNS C70600, EN CW352H) is the default. It is the cheaper of the two grades, widely stocked, and its flow, corrosion and fabrication characteristics cover the great majority of seawater cooling, firewater, bilge, ballast and sanitary systems. The 70/30 grade (UNS C71500) enters the picture when the service is more demanding — higher velocity, higher temperature, more aggressive chemistry, or where a thinner wall is required for the same pressure rating.

Matching Standards to Product Form

A common specification error is to write a single standard into the purchase order and assume it covers all product forms. In practice, Cu-Ni standards are product-form specific:

• EEMUA Publication 144 — the de facto specification for 90/10 seamless and welded tube for offshore applications; widely called out for platform seawater, firewater and utility piping.
• ASTM B466 / B466M — seamless Cu-Ni pipe and tube, the most common US-based reference for shipboard and process piping.
• ASTM B467 — welded Cu-Ni pipe and tube, used where welded construction is acceptable and economic.
• ASTM B111 / B111M — seamless condenser and heat-exchanger tubes, the right reference for power-plant and refinery condensers up to ~80 mm OD.
• EN 12451 — copper and copper alloy seamless tubes for heat exchangers; pairs with EN 1653 for plates used in exchangers.
• JIS H3300, DIN 86019, BS 2871 — regional standards often required by shipyards in Japan, Germany and the UK respectively.
• ISO 13373 — condition monitoring and diagnostics reference used in service-life assessment.

A clean enquiry lists the alloy designation, the product form, the governing standard, the dimension standard (ASME B36.19 for example), the test regime (hydrostatic, eddy current, PMI) and the documentation required (EN 10204 3.1 or 3.2 mill test certificate, third-party inspection by SGS / BV / TÜV / DNV as appropriate).

Where Copper-Nickel Is Specified — and Where It Is Not

Shipbuilding and naval

Cu-Ni 90/10 has been the standard for seawater cooling, firemain, bilge, ballast and sanitary systems on commercial vessels for decades and remains the default for naval surface combatants and submarines. Its biofouling resistance, low corrosion rate in saline service and ease of fabrication make it the most cost-effective material over a full service life. For higher-temperature or higher-velocity applications — condensers, lubricating-oil coolers — 70/30 enters the specification.

Offshore oil & gas

EEMUA 144 90/10 is the workhorse specification for fixed and floating platforms, particularly for firewater ring mains, seawater lift and utility cooling. It welds cleanly, takes shop- and field-bending well, and is tolerant of the splash-zone environment when correctly installed.

Desalination

Multi-stage flash (MSF) and multi-effect distillation (MED) plants use Cu-Ni extensively for evaporator tube bundles, brine heaters and heat-recovery sections. 70/30 is the usual choice where higher temperature and brine concentration push the 90/10 grade beyond its optimum window.

Power generation and refining

Cu-Ni condenser and feedwater-heater tubes (ASTM B111) are common in steam power plants, while refineries use the alloy for hydrocarbon condensers and overhead cooling where chloride-induced SCC of stainless steel is a real risk.

Where it is not the right answer

Cu-Ni is not appropriate for hot, dry, oxidising service above roughly 400 °C; for highly acidic or strongly oxidising media; or where galling or extreme mechanical wear dominate. In those cases, duplex stainless steel, titanium Grade 2 or nickel-base alloys (Alloy 400 / Monel, Alloy 625 / Inconel 625) are the usual alternatives — and a number of those options are also part of the same mill's product range.

Cu-Ni vs Stainless Steel vs Titanium: A Short Engineering Comparison

Specifiers often weigh Cu-Ni 90/10 against 316L stainless steel and commercially pure titanium. The honest answer is that each has a niche:

• Cu-Ni 90/10 — best for general seawater service up to ~4 m/s, where biofouling resistance and low total cost of ownership matter. Good weldability, no preheat or PWHT in most cases.
• 316L stainless — appropriate for clean, lower-velocity freshwater or for short, easily-replaceable spool pieces; vulnerable to pitting, crevice and chloride SCC in warm seawater, and typically requires a higher alloy or a cathodic-protection system to survive in saline service.
• Titanium Grade 2 — outstanding seawater resistance and immunity to chloride pitting/SCC, but more expensive per kilogram and harder to fabricate; preferred for critical coolers in nuclear service and for the most aggressive offshore duties.

For most shipboard and offshore applications, 90/10 Cu-Ni hits the lowest lifecycle cost of the three. For the most demanding duties, titanium pays back. The key is to match the alloy to the actual velocity, temperature, chloride content and inspection regime — not to default on a single material "because we always used it".

Fabrication Notes Worth Knowing Before You Issue the PO

Cu-Ni is straightforward to fabricate, but a few points are worth flagging to avoid field problems:

• Welding. Standard processes are TIG/GTAW, MIG/GMAW, pulsed MIG and SMAW, using Cu-Ni filler metals such as ERCuNi (90/10) or ERCuNi30Fe (70/30). No preheat and no post-weld heat treatment are required for the usual service conditions. Avoid sulphur-containing atmospheres (paint, oil) near hot metal — sulphur embrittles copper-base alloys.
• Bending. Cold bending is preferred for tube up to moderate diameters; hot bending (above ~700 °C) is used for larger pipe and requires neutral or slightly oxidising atmosphere to avoid hydrogen embrittlement.
• Machining. Cu-Ni is "gummy" relative to steel — use sharp carbide tools, positive rake, low cutting speeds, and ample coolant to keep swarf clear.
• Galvanic compatibility. Avoid direct coupling to less-noble metals (carbon steel, aluminium) without isolating gaskets or dielectric unions; Cu-Ni is cathodic in a galvanic couple and will accelerate corrosion of the less-noble partner.
• Cleaning. Internal cleanliness matters; debris left from fabrication can undermine corrosion performance. Specify a clean-and-cap protocol for shipment and storage.

Sourcing From an Integrated Mill: Why It Matters for Project Delivery

On a real project, the alloy is only one piece of the puzzle. The piping package typically includes tube, pipe, butt-weld fittings, flanges, stud bolts, gaskets, valves and often the heat-exchanger tube bundle. Sourcing each from a separate vendor creates coordination risk: mismatched standards, partial deliveries, divergent documentation, and a multiplication of freight and inspection costs.

A single integrated mill that produces the full pressure-boundary package can shorten the critical path, harmonise documentation (one MTC, one test regime, one set of markings) and offer a true project-centric bundled price. This is the model that EZ Steel Industrial has applied since 1994 across its full product range, from carbon steel pipe for high-pressure lines through to stainless steel pipe for process service, copper-nickel for marine and offshore, and the complete fittings / flanges / gasket / stud-bolt / valve bundle that goes with them.

In practice, that integrated approach translates into four operational advantages on a project:

• Single documentation chain. MTCs to EN 10204 3.1, third-party inspection certificates, PMI and hydrostatic test reports all formatted and traceable against a unified project number.
• Coordinated production scheduling. Fittings, flanges and tube can be made in the same production window so that partial deliveries do not stall site erection.
• Full-cycle traceability. From raw-material heat number through forming, heat treatment, NDT and final inspection, the chain is unbroken — important for ASME B31.1 / B31.3, marine class (DNV, LR, ABS, BV) and nuclear-adjacent work.
• Project-bundled pricing. Aggregating volume across a full pressure-boundary package typically delivers a lower landed cost than buying each line item piecemeal.

What a Complete Cu-Ni Package Looks Like

A typical project enquiry for copper-nickel material can extend well beyond tube. Drawing on the EZ Steel Industrial catalogue, a fully bundled package would usually include:

• Tubing and pipe — seamless 90/10 and 70/30 to ASTM B466, B111, EEMUA 144, EN 12451, JIS H3300, BS 2871 or DIN 86019, in OD ranges typically from 6 mm up to 610 mm and schedules 5S / 10S / 40S / 80S.
• Pipe fittings — butt weld fittings in long- and short-radius elbows, equal and reducing tees, concentric and eccentric reducers, caps and stub-ends, plus the matching pipe fittings portfolio (socket-weld and threaded) for smaller-bore connections.
• Flanges — pipe flanges in weld-neck, slip-on, blind and lap-joint executions, in both steel and dedicated copper-nickel flange grades to ASTM, ASME B16.5 / B16.47 and EN 1092-1.
• Bolting and sealing — gasket stud bolt nut assemblies matched to the flange class and service, including spiral-wound, ring-joint and non-asbestos sheet gaskets.
• Heat-transfer side — finned tubes and U bend tubes for the condenser and cooler bundles that sit at the seawater/process interface.
• Valves — industrial valves in gate, globe, check, ball and butterfly executions, body materials selected to match the line — including Cu-Ni and nickel-aluminium-bronze bodies for the wetted seawater side.

A Practical Selection Checklist Before You Send the Enquiry

Before issuing a purchase order for copper-nickel material, it is worth stepping through a short list of questions that catches most specification errors at the desk rather than at the fabrication shop:

• What is the service fluid — clean seawater, polluted seawater, brine, hydrocarbon condensate, freshwater? At what maximum velocity and temperature?
• Which governing standard is mandatory — EEMUA 144, ASTM B466, B111, EN 12451, JIS H3300, a marine class rule (DNV, LR, ABS, BV), or a combination?
• What product forms are in scope — tube only, or tube + fittings + flanges + bolting + valves as a bundled package?
• What documentation is required — EN 10204 3.1, 3.2, third-party inspection, PMI, hydrostatic, NDT (eddy current, ultrasonic, radiographic)?
• What is the delivery window — ex-stock, scheduled mill roll, or full mill production? And does the project allow partial deliveries or require a single shipment?
• What fabrication is needed — cut-to-length, shop bending, weld-prep, special end finishes, custom marking?

A well-prepared enquiry gets a faster, more accurate quotation — and a lower risk of a downstream technical or commercial surprise.

Closing Thoughts

Copper-nickel alloys have earned their place in marine, offshore, desalination and process service because they do a specific job — resisting flowing seawater while staying weldable, fabricable and economically sensible — better than almost any alternative. The grade choice (90/10 vs 70/30), the standard call-out (EEMUA 144, ASTM B466, B111, EN 12451, JIS H3300), the product-form package (tube, fittings, flanges, bolting, valves) and the documentation regime are the four decisions that drive a clean outcome.

A mill that can deliver that full package from a single production chain, with project-bundled pricing and a single documentation set, removes a large slice of coordination risk from the buyer — and is usually the difference between a delivery that lands on time and one that does not.