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.

 

[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.

 

[SeaEric]

I suspect that Poxitar is now classified as a "hazardous material" and is only available to industrial applications. Same as oil based alkyd semi gloss paint which is no longer sold in gallons - only quarts.

 

[BOATER BOB]

I had my 53 SF waterb blasted 7 years ago and filled blisters with System Three pre mixed epoxy that is like peanut butter so it fills good done all blisters one then sanded then again and sanded applied a coat of west epoxy with slow hardner and when it started getting tacky put first coat of interlux then 4 more of barrier coat Interlux then coat of cheap blue bottom paint as a marker then 2 coats of Petit black ablative so far so good.

 

[HahnR]

I had our old boat, an Egg Harbor repaired in 2004. It was sand blasted, filled & faired, barrier coated then bottom coated. No blisters on the boat now 18 years later. My understanding with the coal tar is it cannot be touched up nor can any bottom paint be applied over it. I'm not sure what the antifouling properties of it are either.

I think the biggest advantage is 2 coats does the trick, vs several barrier coats & 2 coats of bottom paint. The information in the Z spar ad is pretty close to what they are telling me. I'm going to continue my research, thanks to everyone for your help and insight.

Randy

 

[warrenw]

If you are looking for alternate suggestions for the yard, I'm having the badly blistered bottom redone on my 47 Commander this spring and I'm going all Pettit:
Pettit EZ Fair (fairing compound)
Pettit Protect Epoxy Primer (barrier coat)
Pettit Horizons Ablative Antifouling

The big difference is that the Pettit Protect Epoxy Primer barrier coat is much thicker than the Interlux Interprotect 2000E, far fewer coats to get the required film thickness therefore savings on labour.

I went this route as Defender had a great sale on the Pettit fairing compound and barrier coat, then sourced the paint here locally in Toronto.

My boat is only in the water half the year so I expect this bottom repair to outlast me.

 

[jim rosenthal]

I would not have a problem using any product by a reputable manufacturer which is specifically intended for marine use, on fiberglass hulls. That would include Poxitar, if you can find it. I'm not sure it's still out there. But from the ad reproduced here, it seems intended for the purpose we are all discussing.

As I said, so far I've had good performance from VC Watertite and Interprotect. Also, when my boat was repowered several years ago, they used walnut shells or soda to clean off the bottom and added a few more coats of IP at that time.

The problem has not been fouling on the hull nearly as much as fouling on the underwater metal parts. Adding more coats of Barnacle Barrier has helped on that.

 

[HahnR]

They use one of the Sherwin Williams products. The service manager says they put it on a Chris Craft fiberglass boat that had a lot of blisters a few years ago. So far so good. They have it on several houseboats that are in the water for 3 - 4 seasons at a time, steel of course, don't leave the slip hardly at all, they have little to no marine growth when they get pulled. No algae buildup or zebra mussels. I'm waiting on an estimate for a minimum of 3 coats of Petit Protect epoxy primer & 2 coats of antifouling paint, then I'll decide what to do. Either way, all the old paint is getting sanded off, blisters filled & faired, & some kind of barrier coat applied.

I had never heard of coal tar epoxy before, never too late to get an education on something. I'm just not real sure that's what I want on our boat yet... I'll keep everyone posted

Randy

 

[bostonhatteras]

https://epoxyproducts.com/coaltar.html
This site no longer sells coal tar epoxy but if you scroll down it offers an informative talk on the what and why of coal tars. The entire site is sort of random but the guy likes to discuss all his products in depth, and they are virtually technical data sheets in discussion format. What i got from it is that coal tars were a cheap alternative with a couple desirable attributes, and more undesirable ones. When planning my bottom job i seriously considered purchasing from this guy as I'm in mass but i used interlux 2000 mainly due to the company's financial wherewithal in case of a product failure.

 

[cww]

I think Eric nailed this one. It was probably a fine product, but petro-carbon based products seem to be on the naughty list for underwater use now. Regular bottom paint has changed so much over the years, when I was a little kid you used to get at least 2-3 years out of it even in Florida. Now you're lucky if you get a year and a half out of the new stuff.

 

[HahnR]

From what I've been able to tell from the data sheets the issue isn't once it's cured & in the water, it's just nasty stuff to work with. You need a guy that's expendable or pretty well suited up to apply it. You need a good respirator and you don't want to get it on your bare skin. Cures fast then you're ready to go

 

[HahnR]

Been meaning to give an update; I decided to go with the coal tar epoxy our marina recommended. Here's a couple of pics leaving the building before she went in this spring