Coal tar epoxy

[HahnR]

OK, last fall when we got pulled, we had the blisters blasted off & the boat has been in inside heated storage all winter, so everything is good & dried out. Now is the time for a barrier coat. Our marina is recommending coal tar epoxy rather than a 2 part epoxy barrier coat and bottom paint. They claim it is a much more durable product and will seal the blisters better than a barrier coat. I had never heard of it before, has anyone ever used it & would you recommend it? Looks like it is more commonly used on steel

Randy

[JD5652]

Never heard of using coal tax epoxy on fiberglass. I've seen it used as a primer coat on aluminum fuel tanks, but that's about it.

Think I would go with regular barrier coat unless there is other evidence that coal tar is actually better.

Can the yard give you some refernces of previous customers that you can check with?

[jim rosenthal]

I think the industry standard for barrier coating after blister repair is either Interprotect, which is a two-part product (I have this on my boat and it has held up very well so far), or vinylester resin (another two part product) or West System epoxy. The usual procedure is to blast off all the loose material, open up all the blisters, allow the hull to dry for weeks if not months, and then fill and fair the blisters (VC Watertite is commonly used) and then apply barrier coat. I have not heard of coal tar epoxy being used on boats such as ours. I don't know how much good it will do to check references as most owners will not be aware if the blister repair is holding up unless the failure of it is very obvious. I think I would ask the manufacturers of coal tar epoxy materials to comment on whether it is suitable for the purpose. If I were in your shoes, which I was years ago, I'd stick to the tried and true materials and methods.

[jim rosenthal]

I could not find any references on CTE being used on fiberglass hulls.

[brettportzer]

Also, as Jim is pointing out, the barrier coat is not necessarily sealing up the blisters, per se...

They need to be properly repaired and then the barrier coat is sealing the now sound hull as a whole.

I had my boat dustless blasted this fall, and I am going to fix up a very few little sections where there is anything funny going on with the laminate, with West System epoxy.

After that, I am going to do a coat of Interprotect 2000E, and then I am going to fair with WaterTite, and then I am going apply the remaining coats of Interprotect.

Alternating coats of white and grey for the Interprotect, and then 1 coat of red ablative, followed by two coats of blue.

Hopefully then just touch up the blue as needed.

Seems to me this is the standard thing.

[Cricket]

Don't know anything about the cold tar product for the blisters, it is good on aluminum tanks.
As far as repairing blisters goes, I think often times too much "putty" gets used instead of building the deep ones back up with fiberglass and resin and then fairing that out with putty.

[SeaEric]

The former owner of the boat yard at Piney Narrows used "Poxitar" exclusively. He claimed it was the best coating. Z-Spar used to have their own branded Poxitar product. I'd do some more research before rejecting the yard's plan.

[ian w]

I had interprotect put on my boat 30 years ago
Not a blister since
Ian w 1881 53 my

[brettportzer]

The former owner of the boat yard at Piney Narrows used "Poxitar" exclusively. He claimed it was the best coating. Z-Spar used to have their own branded Poxitar product. I'd do some more research before rejecting the yard's plan.

PoxitarAd.jpg

[SEVEN]

My bottom was sandblasted and all blisters removed about 10 years ago. There were four coats of barrier coat Applied then. After the 10 year. I have only had two small blisters show up. They were the size of a $.25 piece. They were ground them down dried, patched and four coats applied to those areas. I swear by barrier coat.