Anti-fouling paint

Anti-fouling paint or bottom paint is a specialized coating applied to the hull of a ship or boat to slow the growth of subaquatic 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 antifouling 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 Age of Sail, sailing vessels suffered severely from the growth of barnacles and weeds on the hull, called "fouling". Thin sheets of copper or Muntz metal were nailed onto the hull in an attempt to prevent marine growth. 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. Marine growth affected performance (and profitability) in many ways.

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

Modern antifouling paints

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

"Hard" bottom paints, or "nonsloughing" bottom paints, are made 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 silicone 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, which has been banned in the International Convention on the Control of Harmful Anti-fouling Systems on Ships of the International Maritime Organization due to its serious toxic effects on marine life (such as the collapse of a French shellfish fishery).[4] The Port of San Diego is investigating how to reduce copper input from copper-based antifouling coatings [5] and Washington State has passed a law which may phase in a ban on copper antifouling coatings on recreational vessels beginning in January 2018. [6] However, a similar ban was rescinded in the Netherlands after the European Union's Scientific Committee on Health and Environmental Risks concluded The Hague had insufficiently justified the law. In an expert opinion, the committee concluded the Netherlands government's explanation "does not provide sufficient sound scientific evidence to show that the use of copper-based antifouling paints in leisure boats presents significant environmental risk." [7]

"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][8]

Some innovative bottom paints that do not rely on copper or tin have been developed in response to the increasing scrutiny that copper-based ablative bottom paints have received as environmental pollutants.[9][10][11]

A possible future replacement for antifouling 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 micro-organisms and barnacle larvae.[12][13]

See also

References

  1. ↑ Are foul-release paints for you? Coating calculator, National Fisherman
  2. ↑ Dafforn, Katherine A.; Lewis, John A.; Johnston, Emma L. (2011). "Antifouling strategies: History and regulation, ecological impacts and mitigation". Marine Pollution Bulletin 62 (3): 453–65. doi:10.1016/j.marpolbul.2011.01.012. PMID 21324495.
  3. ↑ 3.0 3.1 3.2 Ecofriendly boating, antifouling paint
  4. ↑ "Focus on IMO - Anti-fouling systems". International Maritime Organisation.
  5. ↑ http://www.waterboards.ca.gov/rwqcb9/water_issues/programs/watershed/souwatershed.shtml
  6. ↑ http://www.tradeonlytoday.com/home/511463-washington-state-bans-copper-bottom-paintdid the same in May, 2011.
  7. ↑ http://www.thefreelibrary.com/EU+expert+committee+challenges+Dutch+copper-paint+restrictions.-a0226476007
  8. ↑ Selecting an anti-fouling paint, West Marine
  9. ↑ http://goliath.ecnext.com/coms2/gi_0199-5573950/Fouling-out-coppers-glory-fades.html Fouling out: coppers glory fades as new bottom-paint research leads to improved antifouling treatments, National Fisherman, June 2006
  10. ↑ "EPA Reports to Congress on Tributyltin Boat-Bottom Paint" (Press release). EPA. June 20, 1997. Retrieved August 26, 2012.
  11. ↑ http://findarticles.com/p/articles/mi_m0BQK/is_6_10/ai_n15858063/ Will California terminate copper paint?, BNET, 2005
  12. ↑ Paul Marks (September 2009). "Slimy-skinned ships to slip smoothly through the seas". New Scientist. Retrieved 28 September 2009.
  13. ↑ "Slime-Covered Boats Could Keep Marine Pests at Bay". 28 September 2009. Retrieved 28 September 2009.

External links