Anti-fouling paint

  1. Pages with broken file links
  2. Paints
  3. Ship construction
  4. Fouling


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Anti-fouling paint or bottom paint is a specialized coating applied to the hull of a ship or boat in order to slow the growth of organisms that attach to the hull and can affect a vessel's performance and durability. Hull coatings may have other functions in addition to their anti-fouling properties, such as acting as a barrier against corrosion on metal hulls, or improving the flow of water past the hull of a fishing vessel[1] or high-performance racing yacht.

History

In the days of the clipper ships, sailing vessels suffered severely from the growth of barnacles and weed on the hull, called "fouling." Thin sheets of copper or Muntz metal were nailed onto the hull in an attempt to prevent marine growth. Fouling affected performance (and profitability) in two ways. First, the maximum speed of a ship decreases as its hull becomes fouled with marine growth. Second, fouling hampers a ship's ability to sail upwind.

The inventor of the anti-fouling paint was Captain Ferdinand Gravert, born in 1847 in Glückstadt (Schleswig-Holstein, now in Germany but then Danish), who sold his chemical formula in 1913 at Taltal, Chile. Captain Alex Gravert has valuable documentation about this.

One famous example of the traditional use of metal sheathing is the clipper Cutty Sark, which is preserved as a museum ship in dry-dock at Greenwich in England. A modern version of this anti-fouling system, Coppercoat, uses an epoxy resin to permanently attach copper to the hull of the boat, helping to prevent marine growth for ten years or more.[2]

Modern anti-fouling paints

In modern times, anti-fouling paints are formulated with toxic copper, organotin compounds, or other biocides-- special chemicals which impede growth of barnacles, algae, and marine organisms.

"Hard" bottom paints, or "non-sloughing" bottom paints, come in several types. "Contact leaching" paints "create a porous film on the surface. Biocides are held in the pores, and released slowly."[3] Hard bottom paints also include Teflon and silicon coatings, which are too slippery for growth to stick. SealCoat systems, which must be professionally applied, dry with small fibers sticking out from the coating surface. These small fibers move in the water, preventing bottom growth from adhering.[3]

Environmental concerns

In the 1960s and 1970s, commercial vessels commonly used bottom paints containing tributyltin (TBT), which has been banned by the International Maritime Organisation due to its serious toxic effects on marine life (such as the collapse of a French shellfish fishery).[4] The Port of San Diego banned copper-based bottom paint on recreational boats in January, 2010[5] and Washington State did the same in May, 2011.[6]

"Sloughing bottom paints", or "ablative" paints, are an older type of paint designed to create a hull coating which ablates (wears off) slowly, exposing a fresh layer of biocides. Scrubbing a hull with sloughing bottom paint while it is in the water releases its biocides into the environment. One way to minimize the environmental impact from hulls with sloughing bottom paint is to have them hauled out and cleaned at boatyards with a "closed loop" system.[3][7]

Some innovative bottom paints that do not rely on copper or tin have been introduced. These products have been developed in response to the increasing scrutiny that copper-based ablative bottom paints have received as environmental pollutants.[8][9][10] One brand, EPaint, which has been used by the US Coast Guard, works by producing hydrogen peroxide in the presence of light.[11]

A possible future replacement for anti-fouling paint may be slime. A mesh would cover a ship's hull beneath which a series of pores would supply the slime compound. The compound would turn into a viscous slime on contact with water and coat the mesh. The slime would constantly slough off carrying away microorganisms and barnacle larvae.[12][13]

See also

References

  1. ↑ Are foul-release paints for you? Coating calculator, National Fisherman
  2. ↑ Coppercoat. 10+ year antifouling
  3. ↑ 3.0 3.1 3.2 Eco-friendly boating. Anti-fouling paint
  4. ↑ "Focus on IMO - Anti-fouling systems". International Maritime Organisation. http://www.imo.org/OurWork/Environment/Anti-foulingSystems/Documents/FOULING2003.pdf.
  5. ↑ San Diego bans copper-based anti-fouling paint, Natalie Bruckner-Menchelli, 5th Jan. 2010
  6. ↑ Washington becomes first state to ban copper paint for recreational boats, 3 Sheets Northwest, May 4, 2011
  7. ↑ Selecting an anti-fouling paint, West Marine
  8. ↑ Fouling out: coppers glory fades as new bottom-paint research leads to improved antifouling treatments, National Fisherman, June 2006
  9. ↑ EPA Reports to Congress on Tributyltin Boat-Bottom Paint, 1997
  10. ↑ Will California terminate copper paint?, BNET, 2005
  11. ↑ ePaint, About the Company, How ePaint Bottom Paints Work
  12. ↑ Paul Marks (September 2009). "Slimy-skinned ships to slip smoothly through the seas". New Scientist. http://www.newscientist.com/article/mg20327275.800-slimyskinned-ships-to-slip-smoothly-through-the-seas.html?DCMP=OTC-rss&nsref=online-news. Retrieved 28 September 2009.
  13. ↑ "Slime-Covered Boats Could Keep Marine Pests at Bay". 28 September 2009. http://blogs.discovermagazine.com/80beats/2009/09/28/slime-covered-boats-could-keep-marine-pests-at-bay. Retrieved 28 September 2009.

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