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 that will degrade and weaken the metal,[1] or improving the flow of water past the hull of a fishing vessel[2] or high-performance racing yacht.
Contents
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 maximum speed of a ship decreases as its hull becomes fouled with marine growth.
- Fouling hampers a ship's ability to sail upwind.
- Some marine growth, such as shipworms, would bore into the hull causing severe damage over time.
- The ship may transport harmful marine organisms to other areas.[3]
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."[4] 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.[4]
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).[5] The Port of San Diego is investigating how to reduce copper input from copper-based antifouling coatings [6] and Washington State has passed a law which may phase in a ban on copper antifouling coatings on recreational vessels beginning in January 2018.[7] 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." [8]
"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.[4][9]
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.[10][11][12]
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.[13][14]
See also
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Are foul-release paints for you? Coating calculator, National Fisherman
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 4.2 Ecofriendly boating, antifouling paint
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ http://www.tradeonlytoday.com/home/511463-washington-state-bans-copper-bottom-paintdid the same in May, 2011.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Selecting an anti-fouling paint, West Marine
- ↑ http://goliath.ecnext.com/coms2/gi_0199-5573950/Fouling-out-coppers-glory-fades.html[dead link] Fouling out: coppers glory fades as new bottom-paint research leads to improved antifouling treatments, National Fisherman, June 2006
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ http://findarticles.com/p/articles/mi_m0BQK/is_6_10/ai_n15858063/[dead link] Will California terminate copper paint?, BNET, 2005
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
External links
- Selecting an anti-fouling paint, West Marine
- Clean Boating Tip Sheet, Selecting a Bottom Paint, .pdf chart, Maryland Dept. of Natural Resources
- Bottom Paint for Racing Boats, Sailing World, 2007
- Are foul-release paints for you? Coating calculator, National Fisherman
- Using Antifouling paint against the Gribble Menace, Teamac Marine Coatings
- Lua error in package.lua at line 80: module 'strict' not found.
