Bottom paint
Encyclopedia
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
or high-performance racing yacht
.
, 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.
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.
, organotin
compounds, or other biocide
s-- 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." 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.
(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). The Port of San Diego
banned copper-based bottom paint on recreational boats in January, 2010 and Washington State did the same in May, 2011.
"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.
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. One brand, EPaint, which has been used by the US Coast Guard, works by producing hydrogen peroxide
in the presence of light.
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.
Biofouling
Biofouling or biological fouling is the undesirable accumulation of microorganisms, plants, algae, or animals on wetted structures.-Impact:...
properties, such as acting as a barrier against corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
on metal hulls, or improving the flow of water past the hull of a fishing vessel
Fishing vessel
A fishing vessel is a boat or ship used to catch fish in the sea, or on a lake or river. Many different kinds of vessels are used in commercial, artisanal and recreational fishing....
or high-performance racing yacht
Yacht racing
Yacht racing is the sport of competitive yachting.While sailing groups organize the most active and popular competitive yachting, other boating events are also held world-wide: speed motorboat racing; competitive canoeing, kayaking, and rowing; model yachting; and navigational contests Yacht racing...
.
History
In the days of the clipper shipsClipper
A clipper was a very fast sailing ship of the 19th century that had three or more masts and a square rig. They were generally narrow for their length, could carry limited bulk freight, small by later 19th century standards, and had a large total sail area...
, sailing vessels suffered severely from the growth of barnacles and weed on the hull, called "fouling." Thin sheets of copper
Copper sheathing
Copper sheathing was the practice of protecting the under-water hull of a ship or boat through the use of copper plates affixed to the outside of the hull. It was pioneered and developed by the Royal Navy during the 18th century.-Development:...
or Muntz metal
Muntz metal
Muntz metal is a form of alpha-beta brass with about 60% copper, 40% zinc and a trace of iron. It is named after George Fredrick Muntz, a metal-roller of Birmingham, England who commercialised the alloy following his patent of 1832....
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.
One famous example of the traditional use of metal sheathing is the clipper Cutty Sark
Cutty Sark
The Cutty Sark is a clipper ship. Built in 1869, she served as a merchant vessel , and then as a training ship until being put on public display in 1954...
, which is preserved as a museum ship in dry-dock at Greenwich
Greenwich
Greenwich is a district of south London, England, located in the London Borough of Greenwich.Greenwich is best known for its maritime history and for giving its name to the Greenwich Meridian and Greenwich Mean Time...
in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. A modern version of this anti-fouling system, Coppercoat, uses an epoxy resin
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
to permanently attach copper to the hull of the boat, helping to prevent marine growth for ten years or more.
Modern anti-fouling paints
In modern times, anti-fouling paints are formulated with toxic copperCopper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, organotin
Organotin
Organotin compounds or stannanes are chemical compounds based on tin with hydrocarbon substituents. Organotin chemistry is part of the wider field of organometallic chemistry. The first organotin compound was diethyltin diiodide, discovered by Edward Frankland in 1849...
compounds, or other biocide
Biocide
A biocide is a chemical substance or microorganism which can deter, render harmless, or exert a controlling effect on any harmful organism by chemical or biological means. Biocides are commonly used in medicine, agriculture, forestry, and industry...
s-- 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." 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.
Environmental concerns
In the 1960s and 1970s, commercial vessels commonly used bottom paints containing tributyltinTributyltin
Tributyltin compounds are a group of compounds containing the 3Sn moiety, such as tributyltin hydride or tributyltin oxide. They are the main active ingredients in certain biocides used to control a broad spectrum of organisms...
(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). The Port of San Diego
Port of San Diego
The Port of San Diego is a self-supporting public benefit corporation established in 1962 by an act of the California State Legislature. In 2007, The U.S. Bureau of Transportation Statistics ranked the Port of San Diego as one of America's top 30 U.S. containership ports bringing in nearly of...
banned copper-based bottom paint on recreational boats in January, 2010 and Washington State did the same in May, 2011.
"Sloughing bottom paints", or "ablative" paints, are an older type of paint designed to create a hull coating which ablates
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
(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.
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. One brand, EPaint, which has been used by the US Coast Guard, works by producing hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
in the presence of light.
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.
See also
- BiofoulingBiofoulingBiofouling or biological fouling is the undesirable accumulation of microorganisms, plants, algae, or animals on wetted structures.-Impact:...
- Biomimetic Antifouling Coatings
- Environmental impact of paintEnvironmental impact of paintThe environmental impact of paint is diverse. Traditional painting materials and processes can have harmful effects on the environment, including those from the use of lead and other additives...
- Copper sheathingCopper sheathingCopper sheathing was the practice of protecting the under-water hull of a ship or boat through the use of copper plates affixed to the outside of the hull. It was pioneered and developed by the Royal Navy during the 18th century.-Development:...
- Muntz metalMuntz metalMuntz metal is a form of alpha-beta brass with about 60% copper, 40% zinc and a trace of iron. It is named after George Fredrick Muntz, a metal-roller of Birmingham, England who commercialised the alloy following his patent of 1832....
- KeelhaulingKeelhaulingKeelhauling is a form of punishment meted out to sailors at sea...
External links
- Selecting an anti-fouling paint, West Marine
- The Basics of Anti-Fouling Paints, BoatZincs.com
- 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
- Port of San Diego supports ongoing research to find effective, non-toxic hull paint
- Anti-fouling paint tips from Eco-Friendly Boating
- All about bottom painting, including 20 min. video, West Marine