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Metals are known to rust when they come into contact with seawater. The issue affects all ships, oil rigs, and even desalination plants, but there is one type of metal that is quite special among the others, especially when it comes to withstanding this issue, and that is copper nickel alloys. This is because copper does not corrode and, once mixed with nickel, becomes even more corrosion-resistant and works at higher temperatures.
This blog will discuss the composition of copper nickel alloys, their types, applications, and certain things you need to know about them when buying them.
The simplest way to describe copper nickel alloys, on the other hand, is as a mixture of copper and nickel along with small amounts of iron and manganese in commercial alloys. In this alloy, the proportion of copper is normally in the range of 70 to 90 percent, while the rest is made up of nickel.
Copper and nickel dissolve into each other completely when alloyed. There isn't a weak boundary layer or a brittle pocket forming somewhere in the mix. So when a mill produces a copper nickel pipe or tube to spec, the composition and mechanical properties should stay consistent across the whole length, not just at the ends where testing usually happens.
Anyone comparing this material against other options in the non-ferrous family might find our earlier piece on alloys of non-ferrous metals worth a read before going further into grades.
Two ratios cover almost everything sold commercially, and both are named after the copper-to-nickel split.
Roughly 90 percent copper, 10 percent nickel, with iron sitting between 1.0 and 1.8 percent and manganese capped around 1 percent. The iron here isn't an afterthought. It helps the protective oxide layer stay stable on the surface once the metal is exposed to seawater, and that layer does most of the corrosion-fighting work.
The amount of copper contained within is 70%, while that of nickel is 30%. The quantities of iron and manganese in this alloy are slightly higher compared to those found in 90/10 alloy. As the amounts of nickel increase, the strength and corrosion resistance increase accordingly, but the price also goes up. Specific values may differ according to standards; thus, verification on paper is needed.
Certain features are often mentioned in the description of this material by engineers.
More on how these properties compare with other material families is covered in our guide to non-ferrous alloy properties.
The production method splits copper nickel into two broad groups, and this matters when specifying a product form.
Rolled or drawn into pipe, tube, plate, sheet, bar, and fittings. Most of the copper nickel pipe used in marine and industrial piping falls into this category, since rolling gives more consistent wall thickness than casting can.
Utilizing casting instead of rolling, this option works well for situations in which forming from rolled metal is difficult or costly. Given the influence of nickel content on several properties, the most commonly selected grades of copper-nickel alloy are 90%, which is composed of 90% copper and 90% nickel, and 70/30, made up of 70% copper and 30% nickel.
The most common selection is the CuNi 90/10 (UNS C70600). This material provides good seawater corrosion resistance and is cheaper than the higher-nickel alloy. You can use it in seawater lines and heat exchanger tubing wherever the general corrosion resistance is a consideration.
The CuNi 70/30 (UNS C71500) improves on the mechanical and corrosion resistance performance of the CuNi 90/10 and is thus used in applications where more difficult conditions exist. The exact temperature and pressure limitations vary with the product type and design code.
There's also a modified 70/30 version, sometimes labelled CuNi30Mn1Fe under EN designation CW354H.
Which standard applies depends on the product form as much as the grade itself.
Projects written to European specifications often reference EN designations and Werkstoff numbers instead. Whichever specification is applicable, all the above requirements must be checked with the Mill Test Certificate of the supplier before any confirmation of the purchase order can be made.
Copper nickel alloys are widely used across industries due to their excellent corrosion resistance, high-temperature strength, and durability. Common nickel alloy applications in industry include chemical processing, power generation, marine engineering, aerospace, oil and gas, and heat exchanger systems.
Seawater cooling systems, condenser tubing, and hull sheathing all use copper nickel because steel simply doesn't hold up as well against corrosion and biofouling over the same service period.
Firewater systems and seawater lift lines need a material that won't fail from continuous saltwater exposure, especially offshore, where sending a repair crew out costs real money and time.
Evaporator tubing sits in hot, concentrated brine almost constantly, which is close to a worst-case scenario for most metals but exactly the kind of condition copper nickel was developed to handle.
Coastal power plants run condenser and heat exchanger tubing in copper nickel for the same reason marine systems do. It transfers heat reliably in seawater for decades without needing replacement.
Copper nickel and other copper alloys also turn up in chemical processing, sugar mills, and paper manufacturing, wherever aggressive fluids need to move through equipment without eating through it too quickly.
It isn't the right choice for every application. Copper nickel costs more upfront than carbon steel and some other options, so the decision usually comes down to weighing that initial cost against how much longer it'll last and how much maintenance it'll save down the line.
Flow velocity is another factor to watch when selecting ferrous and non ferrous alloys. Force the water through the system faster than the material’s rated limits allow, and the oxide coating can wear away faster than it rebuilds, resulting in erosion corrosion. Good system design accounts for flow conditions from the start rather than treating the material as indestructible.
The price of the alloy is based on the quantity of nickel in it. That is the reason why 70/30 is more expensive than 90/10. Copper and nickel are both traded commodities, and therefore their prices vary with time.
Seamless pipe costs more than welded pipe in the same grade. Tighter tolerances and extra testing, such as eddy current testing under ASTM B111, add to the cost as well. Custom sizes that require a new mill run generally cost more than material already available in stock.
In the case of UAE-specific projects, the delivery point, the local availability of stock, shipping costs, documentation, and urgency of delivery can also influence the cost of the project.
Choosing the right copper nickel alloy depends on factors such as the application, corrosion resistance, strength, temperature, and required product form. Whether you choose a copper bar or another copper nickel alloy form, understanding these requirements helps ensure reliable performance and long service life.
If the system runs at standard seawater flow with moderate velocity, 90/10 usually covers it at a lower cost. Higher pressure, faster flow, or elevated temperature is where 70/30 earns the extra money.
Flow velocity must be kept within the limits prescribed for whichever grade is installed. An excess of these levels results in erosion corrosion. Avoid water stagnation where possible and ensure that the water quality level is in accordance with the instructions supplied with the installation.
The flow rate should be kept within the specified limits for the particular grade used. Exceeding the flow rate is by far the leading cause of the occurrence of erosion corrosion. Whenever possible, stagnant water should be avoided, and the water quality specifications should be followed.
Check periodically for pitting or erosion, particularly around bends and tees where turbulence picks up. If dissimilar metals share the same system, check for galvanic compatibility. Getting that pairing wrong is a fast way to accelerate corrosion right at the joint.
Copper Nickel pipes, tubes & fittings are available from Golden Harbour in 90/10 and 70/30 grades for marine, offshore and industrial applications across the United Arab Emirates as well as the rest of the GCC. Every delivery comes with documentation and mill certificates included, so there's no need to chase paperwork after placing the order.
Our technical team works alongside customers on grade selection, standard compliance, and sizing before anything ships. As an experienced supplier of copper nickel alloys, we draw on years of expertise in supplying copper alloys and nickel alloys across the UAE market.
Copper nickel alloys are used a lot in marine work, offshore platforms, desalination plants, power plants, and a few other industries. The reason is simple: this alloy stands up well to seawater corrosion, has enough strength for the job, and isn't too hard to work with.
Choosing between 90/10 and 70/30 depends on several aspects such as the surrounding conditions, rate of water flow, and the amount of pressure required for the project. Before placing an order, it's a good idea to have clarity about several issues: namely your choice of the alloy, the form of the resultant product, its dimensions, and the standards you're interested in, be it ASTM or EN.
You should also pay attention to the speed and chemistry of the water, as these parameters will normally define the beginning of corrosion or erosion issues.
Working with a supplier who possesses extensive knowledge of this material makes the procurement process much easier for UAE projects. The right partner will provide the correct alloys, types of products, and documentation to make sure that the material meets the project requirements.
