Copper-Nickel Alloys - Marine Supreme: Introduction
Copper Applications in Metallurgy of Copper & Copper Alloys
Copper, the noblest of the metals in common use, has excellent resistance to corrosion in the atmosphere and in water. In seawater, the copper-nickel alloys have superior resistance to corrosion coupled with excellent anti-fouling properties needed to meet modern demands economically. This article presents an introduction to the alloys and provides references to many other articles, on line and in print, which contain more information on the alloys' properties and applications.
Copper cladding of wood-hulled warships was introduced in the 18th century to prevent damage by wood-boring insects and worms such as the teredo. It was also discovered that copper prevents biofouling by algae and mollusks. This antifouling property meant that ships could stay at sea for long periods without cleaning. Nelson's successful blockade tactics and subsequent victory at Trafalgar were partly due to the superior speed of his clean-hulled, copper-clad ships.
Many of the underwater wrecks now being explored are found to have their copper alloy fittings largely intact. Pulleys salvaged from the 16th Century Mary Rose would only need to be cleaned of deposits to be still usable (See Mary Rose, this issue of Innovations).
The addition of nickel to copper improves its strength and durability as well as its resistance to corrosion, erosion and cavitation in all natural waters, including seawater and brackish, treated or polluted waters. Copper-nickel alloys also show excellent resistance to stress-corrosion cracking and corrosion fatigue. The added advantage of resistance to bio-fouling make it an ideal material for application in marine and chemical environments such as ship and boat hulls, desalination plants, heat exchange equipment, seawater and hydraulic pipelines, oil rigs and platforms, fish-farming cages and seawater intake screens.
This article discusses typical applications for copper-nickel alloys and presents the reasons for their selection. The two main alloys in this family contain respectively 10% or 30% nickel, as well as small amounts of iron and manganese. Table 1 lists typical international and national standards to which the materials may be ordered in wrought and cast forms. Table 2 lists commonly standardized compositions.
|Standards||Applicable Standard Numbers|
|† A new standard for materials for marine use is being prepared.
Note: This summary covers American (ASTM), European (EN replaces all previous national standards) and International Standards (ISO). It does not cover military standards.
|American Designations||Composition, % (Range or Max)|
|UNS Alloy No.||Cu||Pb||Fe||Zn||Ni (incl Co)||Sn||Mn||Others*|
|*Special limits apply when the product is to be welded.|
|European Designation||Composition, % (Range or Max)|
|*Co max 0.1% is counted as Ni.|
Also in this Issue:
- Copper-Nickel Alloys - Marine Supreme: Introduction
- Copper-Nickel Alloys - Marine Supreme: Types of Copper-Nickel Alloy
- Copper-Nickel Alloys - Marine Supreme: Resistance to Corrosion and Biofouling
- Copper-Nickel Alloys - Marine Supreme: Fabrication
- Copper-Nickel Alloys - Marine Supreme: Applications Information
- Copper-Nickel Alloys - Marine Supreme: Website Articles
- Copper-Nickel Alloys - Marine Supreme: Other References
- Copper-Nickel Alloys - Marine Supreme: Illustrations
- Medical Uses of Copper in Antiquity
- Electric Motors with High Temperature Cuprate Superconductors in the Rotor