Bottom Paint

[billangiep]

Most hard bottom paints (epoxy or modified epoxy) have a recommended min./max. splash time generally from 8hrs. to 60 days. If the 60 day limit has expired it's recommended to sand and repaint. So what happens to the paint after the expired time? Our boat sits higher at the dock than when in cruise mode. I have noticed growth between the old and new water line after a few weeks cruising. I know the paint looses it's affective properties but why? I haven't contacted the manufacture but have done an extensive goggle search, any insight?
Bill,
Trinidad SR

[Fstbttms]

Originally Posted by billangiep

I know the paint looses it's affective properties but why? I haven't contacted the manufacture but have done an extensive goggle search, any insight?

Others may have more accurate knowledge of the exact processes involved, but here is my semi-educated response:

Modified epoxies like Petit Trinidad work by releasing cuprous oxide into the water at a controlled rate while the paint is immersed. When the paint is allowed to be exosed to the atmosphere for a prolonged time, the surface layer of the paint dries to a hard finish and either restricts the movement of water into the paint matrix or the movement of copper out of it, or both. Sanding removes the now-hardened surface layer, exposing fresh paint that can work properly when the boat is splashed.

[billangiep]

Fast, Thanks that makes perfectly good sense but abrading the surface of the new water line doesn't seem to bring the paint back to life? Being exposed to the atmosphere for over a yr. now my guess is the paint is hard through and through.

Our boat sits higher at the dock than when in cruise mode. I have noticed growth between the old and new water line after a few weeks cruising. I know the paint looses it's affective properties but why?