Copper Alloys for Marine Environments – An OverviewCopper alloys used in the marine environment include engineering coppers, copper-nickels (including 90-10, 70-30, and high strength alloys), bronzes, phosphor bronze, gunmetals, aluminum bronzes, silicon bronzes, brasses and copper-beryllium. Copper Alloys for Marine Environments (CDA UK Publication 206, Second Revision, 2013) highlights the properties, applications, corrosion behavior, galvanic behavior, marine biofouling, recyclability and good practices of these copper alloys in the marine environment.
Due to their naturally occurring resistance to seawater corrosion and intrinsic biofouling properties copper-nickel alloys have long been widely used in the components of seawater systems. From offshore oil and gas platforms to power and desalination plants and from commercial shipping to naval shipping, copper-nickel fittings have performed superbly in a host of marine applications. Now, a comprehensive body of information and engineering data, compiled by a team of subject-matter experts on the use of copper-nickel alloys in seawater applications is available from the Copper-Nickel Task Group, a team of representatives from manufacturers of copper-nickel products as well as various specialists in the field metallurgy and marine corrosion.
Alloys of copper and aluminum are known as aluminum bronze and, together with other alloying additions, produce a range of properties that are beneficial to a diverse range of industries. Of these, the nickel aluminum bronze group of alloys is the most widely used. They have been adapted with time to optimize performance and can provide a combination of properties that offer an economic alternative to other types of alloy systems. Nickel aluminum bronzes are available in both cast and wrought product forms and have a unique combination of properties including: excellent wear and galling resistance, high strength and high corrosion resistance.
See also: Alloy C86700 Data Sheet, a nickel aluminum bronze alloy used in screw propellers, thrusters and marine hardware
- Aluminum Bronzes - The aluminum bronzes find widespread applications in desalination plants, in marine, offshore and shipboard hardware and equipment and in non-marine applications as well. They are used where other materials might fail prematurely or would be more expensive to buy or fabricate. Since the alloys comprise a wide range of compositions, alloy selection needs to be carefully considered. Expert advice is always useful.
- Brasses (Cu-Zn)
- Copper-Silicon (Cu-Si) - Copper–silicon has a long history of uses as screws,nuts, bolts, washers, pins, lag bolts, and staples for wooden sailing vessels in marine environments. The alloy is not in high demand today for marine environments. The alloys are often composed of copper, silicon and manganese. The inclusion of silicon strengthens the alloy.
- Beryllium Copper (Be-Cu) - Beryllium copper has high corrosion resistance and exceedingly good biofouling resistance, though its manufacturing is limited these days due to potential health effects of beryllium fume and powder inhalation during manufacturing. Nevertheless, in its age hardened condition, beryllium copper attains the highest strength and hardness of any commercial copper-based alloy.
Engineering Copper (Cu)
Engineering copper has good corrosion resistance in the marine atmosphere and seawater, showing very little pitting or crevice corrosion, together with high resistance to biofouling. Applications include seawater piping, heat exchangers, fuel lines and nails. Copper DHP (Deoxidized High Phosphorus - CW024A) is commonly used for tubing in marine environments. However, other alloys such as aluminum brass or copper-nickels are preferred if flow velocities become too high for copper. When seawater conditions are polluted with ammonia and sulphides, higher corrosion rates or pitting can be experienced.
Review page 6 in Copper Alloys for Marine Environments (CDA UK Publication 206, Second Revision, 2013) for specifications on engineering copper.
References on Copper Alloys for Marine Environments
- Copper Alloys for Marine Environments (CDA UK Publication 206, Second Revision, 2013) [PDF]
- Materials Selection for High Reliability Copper Alloy Seawater Systems Seawater systems are used by many industries such as shipping, offshore oil and gas production, power plants and coastal industrial plants. The main use of seawater is for cooling purposes but it is also used for fire-fighting, oil field water injection and for desalination plants. This paper examines the use of copper alloys to provide high reliability systems covering piping valves, pumps, water boxes and strainers.
- Guidelines for the Use of Copper Alloys in Seawater Copper alloys are widely utilized in the design of seawater systems for their excellent resistance to corrosion and biofouling and many other excellent properties. This paper discusses general guidelines that should be considered when choosing copper alloys for service in a marine environment. Topics discussed include: protective film formation, effects of velocity, seawater cavitation, effects of sulfides, marine biofouling, stress corrosion cracking, galling and sizing resistance, and use in desalination environments.
- Copper Alloys in Seawater: Avoidance of Corrosion (CDA UK Publication 225, 2016) [PDF] Copper alloys have been widely used in seawater and related brines, such as in thermal desalination plants, for many years, generally with excellent results. They are commonly used for piping, valves, pumps and heat exchanger tubing, but have found many other applications. Occasionally there are failures due to corrosion, and in many cases, these could be avoided by following some simple design recommendations, by selecting an alternative copper alloy, or by using a simple preventative strategy. This document covers the most common types of corrosion and shows simple methods to avoid them. If these are implemented at the design stage, it can save a large expenditure after a corrosion failure.
- Shipbuilding Aluminum bronze, manganese bronze, aluminum brass, gunmetal, cupro-nickel and 'Monel' are copper alloys which have long been standard materials for shipbuilding. These copper alloys were introduced largely because of their excellent resistance to corrosion by salt-water and salt-laden atmospheres. They have also found applications where wear resistance greater than pure copper is required.