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, or improving the flow of water past the
hull of a fishing vessel 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 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. The inventor of the anti-fouling paint
was Captain Ferdinand Gravert, born in 1847 in Glückstadt, 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." 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. 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. The Port
of San Diego is investigating how to reduce copper input from copper-based
antifouling coatings and Washington State has passed a law which may phase
in a ban on copper antifouling coatings on recreational vessels beginning in
January 2018. 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." "Sloughing bottom paints", or "ablative"
paints, are an older type of paint designed to create a hull coating which
ablates 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 developed in response to the increasing
scrutiny that copper-based ablative bottom paints have received as
environmental pollutants. 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.
See also Biofouling
Biomimetic antifouling coating Environmental impact of paint
References 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 "Focus on IMO - Anti-fouling systems".
International Maritime Organisation.