Anti-fouling paint

Although commonly discussed as being applied to ships, antifouling paints are also of benefit in many other sectors such as off-shore structures[4] and fish farms.

Starting in the mid-1700s thin sheets of copper and approximately 100 years later, Muntz metal, were nailed onto the hull in an attempt to prevent marine growth.

[6] 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.

[6] One of the first successful commercial patents was for 'McIness', a metallic soap compound with copper sulphate that was applied heated over a quick-drying rosin varnish primer with an iron oxide pigment.

[6] In an official 1900 Letter from the U.S. Navy to the U.S. Senate Committee on Naval Affairs,[9] it was noted that the (British) Admiralty had considered a proposal in 1847 to limit the number of iron ships (only recently introduced into naval service) and even to consider the sale of all iron ships in its possession, due to significant problems with biofouling.

During World War II, which included a substantial naval component, the U.S. Navy provided significant funding[10] to the Woods Hole Oceanographic Institution to gather information and conduct research on marine biofouling and technologies for its prevention.

[12] In modern times, antifouling paints are formulated with cuprous oxide (or other copper compounds) and/or other biocides—special chemicals which impede growth of barnacles, algae, and marine organisms.

In marinas, the river nerite, a brackish water snail, was found to have higher mortality, negative growth, and a large decrease in reproduction compared to areas with no boating.

[20] However, despite the toxic chemistry of bottom paint and its accumulation in water ways across the globe, a similar ban was rescinded in the Netherlands after the European Union's Scientific Committee on Health and Environmental Risks concluded The Hague had insufficiently justified the law.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.

One way to reduce the environmental impact from hulls with sloughing bottom paint is to have them hauled out and cleaned at boatyards with a "closed loop" system.