THE WRITING IS ON THE WALL for copper-based antifouling paint. Washington has become the first state in the U.S.A. to ban its use on boats, with effect from 2018.
Antifouling paint discourages the growth of barnacles and plant life on submersed hulls. If you have a wooden boat, it also discourages marine borers from eating your planks for lunch. Copper became the most favored biocide after 1988 when Congress banned the use of tin-based paint, which proved to be harmful to shellfish. But now there is growing concern that copper, too, is toxic to many forms of sea life.
It used to be easy to understand how copper worked. It was a poison, pure and simple, and the rule of thumb was that the more copper a paint contained, the more effective an antifoulant it was.
Now, new ecologically safe antifoulants are available, usually at much higher prices, but their modus operandi is not as obvious. There is vague talk of formulations with biopolymers and promises of photo-active technology, but the net result is a paint with a seemingly impossible mission—to discourage barnacles and slime without killing other forms of sea life.
Until 2018, however, unless new legislation changes things, there will still be four basic types of copper-based antifouling:
* Sloughing. This paint slowly dissolves over time, exposing fresh copper as it does so.
* Hard epoxy or vinyl. This is a scrubbable paint that allows the biocide to diffuse slowly through the skin.
* Ablative. This is usually a copolymer paint that acts by hydrolysis, or chemical reaction with water, and the scouring action of water flowing past the hull.
* Permanent coating. This is a coat of resin, polyester or epoxy in which millions of tiny pieces of copper metal are suspended, each one individually coated with a thin layer of resin and thus electrically insulated from its mates. New copper is exposed by scrubbing the hull every few months and it’s possible that this system could last the life of the boat. But application is a job best left to the professionals.
A ship is ever in need of repairing.
— John Taylor, A Navy of Landships
There was an old lady of Worcester
Who was often annoyed by a rorcester.
She cut off his head
Until he was dead,
And now he don’t crow like he yorcester.
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