The benefits of Copper Nickel
By Katherine Grace
Copper Nickel, also known as cupronickel or Cu-Ni, is an important group of alloys of base metals Copper and Nickel. An addition of 2 – 45% of Nickel to Copper provides these series of alloys that have a wide array of benefits in a range of industries.
Copper Nickel is a ductile and malleable alloy. Often used for coins in the U.S in particular, the most common alloys 90-10 Copper Nickel and 70-30 Copper Nickel are widely used in engineering, particularly in marine environments, thanks to their excellent resistance to corrosion, pitting and erosion, strength, workability, and weldability. A further unique benefit is the ability to resist microbial induced corrosion, due to this property inherent to copper, in many marine applications.
Keep reading for a summary of these alloys, their benefits in detail, in which industries they are utilised and why.
Most common alloys
The most common Copper Nickel alloys are 90-10 Copper Nickel and 70-30 Copper Nickel. The details of these are the following:
90-10 Copper Nickel (90-10 Cu-Ni):
Copper: 86.0 – 89.7%
Nickel: 9.0 – 11.0%
Iron: 1.0 – 2.0%
Manganese: 0.3 – 1.0%
70-30 Copper Nickel (70-30 Cu-Ni):
Copper: 65.5 – 70.1%
Nickel: 29.0 – 32.0%
Iron: 0.5 – 1.5%
Manganese: 0.4 – 1.0%
The applications of these two common alloys include:
Seawater cooling and firewater systems,
heat exchangers, condensers, and piping,
platform riser and leg sheathing,
boat hulls,
oil coolers,
hydraulic tubing,
antimicrobial touch surfaces.
Higher proportions of other metals can also be added to Copper Nickel, which will result in different properties and thus uses.
Copper Nickel Chromium (Cu-30Ni-Cr):
Uses:
Forgings,
cast seawater pumps,
valve components.
Copper Nickel Aluminium (Cu-Ni-Al):
Uses:
Shafts and bearing bushes,
bolting,
pump and valve trim,
gears,
fasteners.
Copper Nickel Tin (Cu-Ni-Sn):
Uses:
Bearings and drill components,
Subsea connectors,
valve actuator stems,
lifting nuts,
ROV lock-on devices,
seawater pump components.
Benefits
Copper Nickel has benefits that apply to most industries and uses.
Easy to Fabricate
Hot and cold working techniques can be used.
Because of the good ductility of the alloy, cold working is normally preferred.
Development of a Corrosion Resistant Surface
Copper Nickel develops a protective film in six to eight weeks, making it corrosion resistant.
Contact with other less noble metals or with cathodic protection systems must be avoided to ensure its development.
Lack of Stress Corrosion Cracking
Copper Nickel alloys do not suffer the stress-corrosion problems associated with some other materials, such as brass and certain zinc alloys.
Along with these, Copper Nickel is used extensively in seawater due to its excellent range of benefits countering the issues present in these environments.
Resistance to Corrosion in Seawater
Copper Nickel alloys have excellent resistance to the high salinity of marine and seawater environments.
Resistance to Biofouling
Biofouling, or biological fouling, is the accumulation of microorganisms, plants, algae, or small animals that cause surface degradation of metals and other materials in seawater or freshwater environment.
The protective surface film which forms naturally on Copper Nickel provides an inhospitable surface to deter marine growth, preventing this degradation.
Resistance to Crevice Corrosion
Crevice corrosion can occur in components in seawater when they are locally starved of oxygen at a joint or under attached biofouling.
Copper Nickel alloys have increased crevice corrosion resistance where other metals can be susceptible to corrode under these conditions.
Excellent durability
Copper Nickel alloys can last decades even in seawater environments.
This benefit also makes Copper Nickel a cost-effective option over a ship’s lifetime.
Uses
Shipbuilding and Repair
The 90-10 and 70-30 Copper Nickel alloys were originally developed for naval condensers and seawater piping more than 60 years ago and are still used in many of the world’s navies.
They are also used on FPSOs (Floating production storage and offloading vessels) and in commercial shipping.
On ships, seawater is used for cooling, tank cleaning and heating, ballast, waste disposal, firefighting and, through distillation, as a source of fresh water for boiler feed water and sanitary hot and cold water.
All require piping systems that consist of Pumps, Valves, Pipe and Fittings. For cooling systems, heat exchangers are also required.
Applications for Copper Nickel alloys can therefore include:
condensers,
coolers and other heat exchangers,
onboard seawater desalination plants,
systems for compressed air,
sanitary systems,
bilge,
ballast water,
brine,
fire mains and sprinklers,
fuel oil,
lube oil,
warm water heating,
grey and black water,
hydraulic lines,
tank heating,
sheathing or plate for boat hulls.
Offshore Oil and Gas
As well as FSPOs, Copper Nickel alloys are used on offshore Oil & Gas platforms in seawater, cooling, and firewater/deluge systems.
They are favoured in warmer climates for their resistance to chloride crevice corrosion and stress corrosion cracking.
Multiple Effect Distillation (MED) plants
There are two types of MED plants; one uses thermos-compression distillation (TCD), the other mechanical vapour compression (MVD).
There can be several evaporator stages and a final heat rejection section.
Copper Nickel alloys are the primary choice for tubes in the evaporator sections.
They are also sometimes used in the final heat recovery exchanger.
Power generation
Generating electricity in both nuclear and fossil-fuelled power plants involves important heat transfer processes;
steam generators,
heat exchangers,
coolers,
condensers,
tanks,
Pipework,
Valves and Fittings.
Copper Nickel alloys are well-suited for these applications, as they can be used successfully in a range of environments, including clean seawater with high-total dissolved solids, brackish water, fresh water, and cooling tower water.
Get your hands on it!
Stirlings is a specialist supplier of Copper Nickel products for use in all of the above!
We stock DIN 86019 10-14 Bar pressure rated Pipe, Fittings & Flanges ranging from 16mm to 219mm, as well as Copper Nickel Plate in the following thicknesses:
6mm
10mm
12mm
16mm
20mm
See our stock right here!
A rhyme for your time
If you want seawater’s greatest foe, make sure to give Copper Nickel a go!
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