Last time we talked about what fouling is and what kind of creatures like to set up shop on the underside of your boat. As you’ll recall a big tool in the toolbox is the use of anti-fouling paint, which is interesting in and of itself. I say tool because the best you can do is keep up with fouling problems–nothing is a silver bullet for this age-old nautical annoyance. Anti-fouling paint can definitely help you reduce your cleaning chores and it should be applied every other year.
As I mentioned, copper in one of its forms is normally used in the paint as the biocidal active ingredient. Tin was found to be more effective, although it’s widely banned because it was found to be damaging to shellfish. There are four common types of anti-fouling paint:
1. Ablative. As the name implies, ablative paint gradually erodes away, uncovering a new copper surface over time. The new exposure to copper keeps it effective over time. The erosion is caused by both chemical reaction of the copper molecules with water molecules, as well as the mechanical action of the water rushing past. This paint is 100% effective as long as it remains on the boat. It is quite expensive (copper is expensive) and needs two coats minimally, preferably more.
2. Sloughing. This is similar to ablative paint but comes off in big flakes instead of on a smaller particle level. It’s less costly but loses effectiveness more quickly.
3. Modified epoxy. With this kind, the copper wears away, not the paint. Copper in the epoxy gradually dissovles and allows the water to penetrate deeper and deeper until all the biocide is depleted. Not a good choice if your boat is out of the water a lot; it loses its effectiveness quickly under those conditions, but it’s a great choice if your boat’s in the water year-round.
4. Vinyl. This works similarly to epoxy. If you have a racing boat, you can make a shiny smooth finish of it. It’s a fussy paint though–its solvents can damage other components of the coat and cause blistering.