Ronald Raygun wrote:

... presumably the length of time a coating stays effective is mainly
related to the rate at which the active ingredients leach out of the
paint (or the paint itself erodes), and this only happens when
immersed ...

Many years ago during my incarnation as a chemist I did business with some
of the largest manufacturers in northern New Jersey. I can say with
certainty that that period often reminds me of outtakes from The Sopranos.

But to "Ronald's" point, depending on the type and composition of the paint,
the antifouling properties can be adversely affected by prolonged dry
storage. While manufacturers can say what they wish in their advertising,
these paints are basically very crude mixtures that rely on the most basic
ingredients for their effectiveness. In the US environmental concerns have
essentially eliminated some of the really effective ingredients that once
provided big advances in antifouling. Now we are back to something similar
to what was used in the 18th century. The main differences are that the can
is better looking and the price is through the roof.

--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://home.comcast.net/~kerrydeare