Copper alloys in aquaculture
What sets copper alloys apart from the other materials used in fish farming is that copper alloys are
In the
In addition to their antifouling benefits, copper alloys have strong structural and
It is the combination of all of these properties – antifouling, high strength, and corrosion resistance – that has made copper alloys a desirable material for such marine applications as condenser tubing, water intake screens,
Growth of aquaculture
Much has been written about the degradation and depletion of natural fish stocks in
Aquaculture, an industry that has emerged only in recent decades, has become one of the fastest growing sectors of the world food economy.[2] Aquaculture already supplies more than half of the world's demand for fish.[12] This percentage is predicted to increase dramatically over the next few decades.
The problem of biofouling
The biofouling process begins when
Biofouling has strong negative impacts on aquaculture operations. Water flow and
Biofouling adds enormous weight to submerged fish netting. Two hundredfold increases in weight have been reported.
To combat
To treat diseases in fish raised in biofouled nets, fish stocks are administered
Antifouling coatings are often used on nylon nets because the process is more economical than manual cleaning.
Biofouled nets are replaced after several months of service, depending on environmental conditions, in a complicated, costly, and labor-intensive operation that involves divers and specialized personnel. During this process, live fish in nets must be transferred to clean pens, which causes undue stress and
A line of net cleaners is available for in-situ washings where permitted.
The aquaculture industry is addressing the negative environmental impacts from its operations (see
Antifouling properties of copper alloys
In the aquaculture industry, sound animal husbandry translates to keeping fish clean, well fed, healthy, and not overcrowded.[41] One solution to keeping farmed fish healthy is to contain them in antifouling copper alloy nets and structures.[42]
Researchers have attributed copper's resistance to biofouling, even in temperate waters, to two possible mechanisms: 1) a retarding sequence of colonization through release of antimicrobial copper ions, thereby preventing the attachment of microbial layers to marine surfaces;[43] and, 2) separating layers that contain corrosive products and the spores of juveniles or macro-encrusting organisms.[44]
The most important requirement for optimum biofouling resistance is that the copper alloys should be freely exposed or electrically insulated from less noble alloys and from
As temperatures increase and water
Corrosion behavior of copper alloys
Copper alloys used in sea water service have low general corrosion rates but also have a high resistance to many localized forms of corrosion. A technical discussion regarding various types of corrosion, application considerations (e.g., depth of installations, effect of polluted waters, sea conditions), and the corrosion characteristics of several copper alloys used in aquaculture netting is available (i.e., copper-nickel, copper-zinc, and copper-silicon[46]).
Early examples of copper sheathing
Prior to the late 1700s, hulls were made almost entirely of wood, often white oak. Sacrificial planking was the common mode of hull protection. This technique included wrapping a protective 1/2-inch thick layer of wood, often pine, on the hull to decrease the risk of damage. This layer was replaced regularly when infested with marine borers.[47] Copper sheathing for bio-resistant ship hulls was developed in the late 18th century. In 1761, the hull of the British Royal Navy's HMS Alarm frigate was fully sheathed in copper to prevent attack by Teredo worms in tropical waters.[48] The copper reduced biofouling of the hull, which enabled ships to move faster than those that did not have copper sheathed hulls.
Environmental performance of copper alloy mesh
Many complicated factors influence the environmental performance of copper alloys in aquaculture operations. A technical description of antibiofouling mechanisms, fish health and welfare, fish losses due to escapes and predator attacks, and reduced life cycle environmental impacts is summarized in this reference.[49]
Types of copper alloys
Copper–zinc brass alloys are currently (2011) being deployed in commercial-scale aquaculture operations in Asia, South America and the US (Hawaii). Extensive research, including demonstrations and trials, are currently being implemented on two other copper alloys: copper-nickel and copper-silicon. Each of these alloy types has an inherent ability to reduce biofouling, pen waste, disease, and the need for antibiotics while simultaneously maintaining water circulation and oxygen requirements. Other types of copper alloys are also being considered for research and development in aquaculture operations.
The University of New Hampshire is in the midst of conducting experiments under the auspices of the International Copper Association (ICA)
Copper–zinc alloys
The Mitsubishi-Shindoh Co., Ltd., has developed a proprietary copper-zinc brass alloy, called UR30,[51] specifically designed for aquaculture operations. The alloy, which is composed of 64% copper, 35.1% zinc, 0.6% tin, and 0.3% nickel, resists mechanical abrasion when formed into wires and fabricated into chain link, woven, or other types of flexible mesh. Corrosion rates depend on the depth of submersion and seawater conditions. The average reported corrosion rate reported for the alloy is < 5 μm/yr based on two- and five-year exposure trials in seawater.[52]
The Ashimori Industry Company, Ltd., has installed approximately 300 flexible pens with woven chain link UR30 meshes in Japan to raise
To date, in over 10 years of aquaculture experience, chain link mesh fabricated by these brass alloys have not suffered from
Copper–nickel alloys
Copper–nickel alloys were developed specifically for seawater applications over five decades ago. Today, these alloys are being investigated for their potential use in aquaculture.
Copper–nickel alloys for marine applications are usually 90% copper, 10% nickel, and small amounts of manganese and iron to enhance corrosion resistance. The seawater corrosion resistance of copper–nickel alloys results in a thin, adherent, protective surface film which forms naturally and quickly on the metal upon exposure to clean seawater.[53]
The rate of corrosion protective formation is temperature dependent. For example, at 27 °C (i.e., a common inlet temperature in the Middle East), rapid film formation and good corrosion protection can be expected within a few hours. At 16 °C, it could take 2–3 months for the protection to mature. But once a good surface film forms, corrosion rates decrease, normally to 0.02–0.002 mm/yr, as protective layers develop over a period of years.
Copper–silicon alloys
Copper–silicon has a long history of use as
As with the copper–nickel alloys, corrosion resistance of copper–silicon is due to protective films that form on the surface over a period of time. General corrosion rates of 0.025–0.050mm have been observed in quiet waters. This rate decreases towards the lower end of the range over long-term exposures (e.g., 400–600 days). There is generally no pitting with the silicon-bronzes. Also there is good resistance to erosion corrosion up to moderate flow rates. Because copper–silicon is weldable, rigid pens can be constructed with this material. Also, because welded copper–silicon mesh is lighter than copper-zinc chain link, aquaculture enclosures made with copper–silicon may be lighter in weight and therefore a potentially less expensive alternative.
Luvata Appleton, LLC, is researching and developing a line of copper alloy woven and welded meshes, including a patent-pending copper silicon alloy, that are marketed under the trade name Seawire.
See also
- Antimicrobial copper-alloy touch surfaces
- Antimicrobial properties of copper
- Antimicrobial properties of brass
References
- ^ Offshore Aquaculture in the United States: Economic considerations, implications, and opportunities, U.S. Department of Commerce, National Oceanic & Atmospheric Administration, July 2008, p. 53
- ^ PMID 15596168.
- ^ "Commercial and research fish farming and aquaculture netting and supplies". Sterlingnets.com. Archived from the original on 28 November 2010. Retrieved 16 June 2010.
- ^ "Aquaculture Netting by Industrial Netting". Industrialnetting.com. Archived from the original on 29 May 2010. Retrieved 16 June 2010.
- ^ Southern Regional Aquaculture Center at "Archived copy" (PDF). Archived from the original (PDF) on 19 November 2010. Retrieved 15 August 2011.
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- ^ The State of World Fisheries and Aquaculture (SOFIA), Biennial Report, 2005 Archived 5 August 2009 at the Wayback Machine, as summarized in Food and Agriculture Organization of the United Nations
- ^ The Next Seafood Frontier: The Ocean, 28 April 2009, references article by Myers in Nature
- ^ Alessandra Bianchi (28 April 2009). "The next seafood frontier: The open ocean – Apr. 28, 2009". Money.cnn.com. Retrieved 16 June 2010.
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- ^ Half of Fish Consumed Globally Is Now Raised on Farms, Study Finds Science Daily, 8 September 2009
- ^ Design Guide: Copper Alloy Mesh in Marine Aquaculture, International Copper Research Association Inc. (INCRA), 1984
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- ^ Ahlgren, M.O., (1998), Consumption and assimilation of salmon net pen fouling debris by the red sea cucumber Parastichopus califormicus: Implications for poly-culture, Journal of the World Aquaculture Society, Vol. 29, pp. 133–139
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- ^ a b c Alberto, Jose and Disselkoen, Ochoa (2009), Floating device to clean nets, Patent application 12/455,150, Publication US 2010/0006036 A1, Filing date 27 May; and National Chilean Patent Application No. 1565-2008 filed on 29 May 2008
- ^ Paclibare et al., (1994), Clearing of the kidney-disease bacterium Renibacterium salmoninarum from seawater by the blue mussel Mytilus edulis, and the status of the mussel as a reservoir of the bacterium, Diseases of Aquatic Organisms, Vol. 18, pp. 129–133
- ^ Enright, C., (1993), Control of fouling in bivalve aquaculture, World Aquaculture, Vol. 24, pp. 44–46
- ^ Lee et al., (1985), Observations on the use of antifouling paint in netcage fish farming in Singapore, Singapore Journal of Primary Industries, Vol. 13, pp. 1–12
- ^ Idema Net Cleaning Systems
- ^ Offshore Aquaculture in the United States: Economic Considerations, Implications, & Opportunities, U.S. Department of Commerce, National Oceanic & Atmospheric Administration, July 2008
- ^ "Copper Nickel : References". Copper.org. Archived from the original on 28 August 2013. Retrieved 16 June 2010.
- ^ Sutherland, I.W., 1983, Microbial exopolysaccarides: Their role in microbial adhesion in aqueous systems, Critical Reviews in Microbiology, Vol. 10, pp.173–201
- ^ a b Edding, Mario E., Flores, Hector, and Miranda, Claudio, (1995), Experimental Usage of Copper-Nickel Alloy Mesh in Mariculture. Part 1: Feasibility of usage in a temperate zone; Part 2: Demonstration of usage in a cold zone; Final report to the International Copper Association Ltd.
- ^ Powell, Carol and Stillman, Hal (2009), Corrosion behavior of copper alloys used in marine aquaculture Archived 24 September 2013 at the Wayback Machine
- ^ "Corrosion Behaviour of Copper Alloys used in Marine Aquaculture" (PDF). Archived from the original (PDF) on 24 September 2013. Retrieved 16 June 2010.
- ^ Copper Sheathing; GlobalSecurity.org; http://www.globalsecurity.org/military/systems/ship/copper-sheathing.htm
- ^ Old Copper; "HMS Victory Copper Sheathing". Archived from the original on 18 May 2011. Retrieved 23 July 2010.
- ^ Environmental Performance of Copper Alloy Mesh in Marine Fish Farming: The Case for Using Solid Copper Alloy Mesh
- ^ "Welcome to CopperInfo – Your Worldwide Copper Information Source". Copperinfo.com. Retrieved 16 June 2010.
- ^ Craig Craven. "UR_Chemicals". Mitsubishi-shindoh.com. Archived from the original on 14 July 2011. Retrieved 16 June 2010.
- ^ a b EcoSea Farming S.A.
- ^ "Copper Nickels : Seawater Corrosion Resistance and Antifouling". Copper.org. 15 December 2005. Archived from the original on 16 August 2013. Retrieved 16 June 2010.
- ^ The Application of Copper-Nickel Alloys in Marine Systems, CDA Inc. Seminar-Technical Report 7044-1919, 1996; http://www.copper.org/applications/cuni/txt_swater_corrosion_resistance.html Archived 16 August 2013 at the Wayback Machine
- ^ http://www.luvata.com; Seawire is a trademark of Luvata Appleton, LLC. The company intends to market a wide range of alloys in addition to copper-silicon under this trademark
Other references
- Design Guide: Copper Alloy Mesh in Marine Aquaculture, 1984, International Copper Research Association (INCRA) 704/5.
- Metal Corrosion in Boats, Nigel Warren and Adlard Coles, Nautical, 1998.
- Galvanic Corrosion: A Practical Guide for Engineers, R. Francis, 2001, NACE Press.
- Marine Corrosion Causes and Prevention, F. LaQue, John Wiley and Sons, 1975.
- The Selection of Materials for Seawater cooling Systems: A Practical Guide for Engineers, R. Francis, 2006, NACE Press.
- Guidelines for the Use of Copper Alloys in Seawater, A. Tuthill. 1987. CDA/ Nickel Institute Publication.
- The Brasses: Properties and Applications, CDA UK Publication 117.
- Copper in the Ocean Environment, Neal Blossom, American Chemet Corporation.
- ICA Project 438: Experimental usage of copper nickel alloy mesh in aquaculture, Mario E. Edding, Hector Flores, Claudio Miranda, Universidad Catholica del Norte, July 1995
External links
- M.S. Parvizi, A. Aladjem and J. E. Castle, "Behaviour of 90–10 Cupronickel in Sea Water," International Material Reviews 1988, Vol. 33, No. 4., ISSN 0950-6608; Available at http://www.ingentaconnect.com/content/maney/imr/1988/00000033/00000001/art00008
- Efird and Anderson, "Sea Water Corrosion of 90–10 and 70-30 Cu-Ni C 14 Year Exposures," Materials Performance, November 1975, ISSN 0094-1492; Abstract available at http://tris.trb.org/view.aspx?id=35723. Entire article available by subscription with National Association of Corrosion Engineers International at http://web.nace.org/Login.aspx?ReturnUrl=%2fdepartments%2fpublications%2fmpvolumes.aspx[permanent dead link])
- Information on Cu-Ni alloys
- Corrosion in aquaculture Archived 28 August 2013 at the Wayback Machine
- Kampachi Farms Aquapod; uses brass mesh and is free-floating (connected with wire)