IF one needs to remove an old epoxy barrier coat (that has has peeled off to a degree, leaving the gelcoat exposed), what is the best way to do it ?? Soda blasting ?? Dry ice blasting ?? Some other method ??
I don’t believe that sanding (which might take days and make a gigantic, toxic mess) is the best solution.
Presently, my buddy’s Nonsuch has anti-fouling on top of the existiing old barrier coat but, as stated, there are bare patches where the barrier has slaked off.
I believe there are some peeling processes that involve relatively high-tech machinery peeling very thin layers off, and there might be some other approaches if the barrier coat’s slaking off because it didn’t adhere well. But, it might be worthwhile to find out why the barrier coat is coming off first.
Are you really asking on behalf of “a buddy” or did you buy another boat and are just embarrassed to admit it?
I’m very embarrassed to admit that I am actually asking on behalf of someone else. But here’s a follow-up question: What’s happened is that a few bare patches have appeared in the keel area, each around 9" square. The white gelcoat shows through. One can get a paint scraper under and “flake” away bits from the edges of the bare patch. I think that it’ll reach a point where the old barrier coat will be solid. At that point, could one carefully sand just around the edges of the bare patch and re-coat the bare area with new barrier coat ?? This is as opposed to (yikes !!!) stripping the entire hull. The barrier coat looks rock-solid on the hull.
When I bought my 30 back in ‘03, I had it peeled and then I applied the appropriate epoxy coats and then the appropriate barrier coats before the bottom paint. The barrier paint has never come off, so I would agree that it may not have been applied properly or the bottom was not prepared the right way. I use ablative bottom paint and it sloughs off every couple of years. I sand a little and re-apply.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
If the barrier coat has flaked off in some spots, the rest can’t be trusted and should be removed.
Further more,
Most - if not all epoxy barrier coatings can not be applied on a moist surface. If not dry, it will not hold. That means that after the hull has been brought back to gelcoat, it should be measured for moisture before opening the bins of epoxy. When moist, it needs to dry out (over winter).
I support the soda blasting approach as does Practical Sailor. A local fellow came in at 7:00 a.m. draped the area blasted down to gel coat, cleaned up and was gone by 3:00 p.m. I don’t know if he used glass or soda.
I also agree with the soda blasting solution. When they peeled mine, I thought they were damaging the hull and I wish that soda blasting was available. But the peeling did work!
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Soda blasting is the best removal option. However it will not yield the right surface profile, you’ll need to check the barrier coat specs but generally the hull needs to be 80 grit smooth.
