Best epoxy barrier coat?

[ranger58sb]

I'm considering a soda blast/barrier coat/bottom paint project for next Winter/Spring (2026-2027), and have begun research on process, time/labor, costs, etc... and best products to use for the barrier coating part of all that. Starting thought early, 'cause I know it'll be a big budget thing.

We had the boat last stored on land over the Winter of 2021-2022, so I reckon it's time to let the hull dry out again... and I suspect it's also (past?) time to remove all the successive layers of bottom paint over the boat's lifespan and start over again. I'm focused mostly on the fiberglass, but we also have a boatload of hydraulic swim platform hardware down there, too...

Initial general research returns lots of hits on TotalBoat TotalProtect Epoxy Barrier Coat... but so many are illustrated with the same chart diagram... that it looks more like paid advertising instead of honest and unbiased reporting. ??? Interlux InterProtect 2000E seems to get OK reviews. Practical Sailor also mentions Pettit Protect, and Sherwin-William's Seaguard.... but the latter seems to just be pre-mixed paints. Others?

Have folks here done a similar project? Comments, pitfalls, recommendations? Products with best results? General insight into costs? (Won't be doing the painting myself, so I know labor costs will be the largest cost component with big variables like number of coats and labor rates, etc...)

-Chris

 

[sean9c]

InterProtect is the OG, I'd go with that. Follow the instructions on the can.

 

[Comodave]

I have used Interprotect 2000 on multiple boats, like 8 or so, since the early 90s and always had good results.

 

[Mac2]

+1 for Interprotect

 

[ranger58sb]

InterProtect is the OG, I'd go with that. Follow the instructions on the can.

OG?

 

[Frosty]

Just a "hip" way of saying it's the original, I believe.

 

[BruceK]

When I inquired, fairly sure the yard was recommending vinylester, commonly used on new builds as the outer surface.
Waiting on my job being scheduled, the Yard is set up to do the work, but it only does 12 a year.

 

[Comodave]

Why would they use vinylester instead of epoxy? Maybe cheaper but the cost is mostly labor not materials. So I want the best protection that I can get and I think epoxy is better. Some boat builders use vinylester resin in the first few layers of glass because it is better for blister protection and cheaper than epoxy.

 

[BruceK]

Why would they use vinylester instead of epoxy? Maybe cheaper but the cost is mostly labor not materials. So I want the best protection that I can get and I think epoxy is better. Some boat builders use vinylester resin in the first few layers of glass because it is better for blister protection and cheaper than epoxy.

I think your italicized words above answer your question. An extensive bottom job is often blister related, avoiding recurrence is a strong consideration.

 

[Comodave]

I think your italicized words above answer your question. An extensive bottom job is often blister related, avoiding recurrence is a strong consideration.

Ok, I am at a loss. What italicized words are you referring to? I didn’t italicize anything as far as I know.

 

[BruceK]

Ok, I am at a loss. What italicized words are you referring to? I didn’t italicize anything as far as I know.

You didn`t. I did, when quoting your post.

 

[Comodave]

Ok, but that is referring to the original boat construction not a barrier coat on the outside of the bottom. Builders use vinylester to help protect and it is cheaper than epoxy which actually protects better than vinylester. But if they were to use epoxy in the original build they would have to use epoxy all the way through since other resins won’t stick to the epoxy. But for a barrier coat why not just use epoxy since it is superior to vinylester for blister protection. The cost differential wouldn’t be that great not to go for the best protection.

 

[psneeld]

Vinylester is used as the last several coats of resin in the construction as far as I know to protect from water absorption.

Barrier coats are a further step but sometimes considered less important with boats using vinylester in their construction.

Interprotect supposedly has the mineral "mica" in it an claims it's overlapping "microplates" help waterproof the coating/bottom even more.

I love Interprotect as a primer for many things as it is a pleasure to work with despite its price and fairly ridged application.

If one plans to use Interlux bottom paint, the application of Interprotect and bottom paint at the correct interval provides a superior bond.

 

[ranger58sb]

Why would they use vinylester instead of epoxy? Maybe cheaper but the cost is mostly labor not materials. So I want the best protection that I can get and I think epoxy is better. Some boat builders use vinylester resin in the first few layers of glass because it is better for blister protection and cheaper than epoxy.

I think your italicized words above answer your question. An extensive bottom job is often blister related, avoiding recurrence is a strong consideration.

Reading suggests vinylester is better than bare gel coat for blister protection, but not better than epoxy.

Thanks for bringing it up, though. I think useful to have considered that in the mix... even though I know I want to use epoxy for my project.

-Chris

 

[Gdavid]

I'm a fan of Blue Water brand products including their epoxy barrier product "Bottom Protect". I've also used Interprotect 2000 on multiple occasions and they are about the same in application and effectiveness, but the Blue Water products are less expensive. In all cases the barrier was applied as a precaution to a soda blasted or sanded gelcoat surface. I order directly from Blue Water for my bottom paint as well, I have had good experience with their Copper Shield 45 ablative in the Chesapeake bay waters.

 

[psneeld]

Chris, what year is your boat?

After about 2000, many vessels built to ABYC standards and used some Vinyester in their construction.

I would still add a barrier coat while I was doing what you are and plan on keeping the boat more than just a few years.

 

[ranger58sb]

Chris, what year is your boat?

After about 2000, many vessels built to ABYC standards and used some Vinyester in their construction.

I would still add a barrier coat while I was doing what you are and plan on keeping the boat more than just a few years.

2006, with vinylester... but yep, I agree about adding epoxy barrier coat. Especially since it's about time to start over with the bottom paint, and the epoxy coating just seems to be the right way to do it for a 'glass boat at this age...

Others have predicted I'll gain maybe a knot or two at top speed, but I don't really care about that...

Not sure I even really believe it all that much, anyway, although I know the boat made 31 kts sometime in its past (but after 2016) and I only make 29 kts at WOT now. I guess the bottom could have some slight impact, but I'd also guess more recent load profile and more recent prop tuning would have more impact than the number of layers of old/new bottom paint...

And besides, we mostly run at trawler speeds when we can, and seldom at more than 18-20 kts if we have to get up on plane... so a potential additional 1-2 knots more at the top end isn't much of an attraction.

-Chris

 

[O C Diver]

I think Sean used Interlux for barrier coat. The hull was completely sandblasted below the waterline to address a couple of issues.

When it came to the barrier coat Sean took a different approach. If you read the coating specifications, there is a prescribed thickness for it to be totally effective. So Sean did four coats of alternating colors to achieve the thickness. Using alternating colors allows you to see any areas you may have missed.

Considering your investment in this project, the additional cost for four coats is probably minimal. Below is the post from my refit thread covering the barrier coating.

My Short Haul Refit

OC, I am awestruck! I don't think I have the words to describe the beauty you have produced with all your hard work. Outstanding Job! :blush: Thanks! I'm really more the mechanical part of the team. Sean is the glass and paint man. He makes everything look purdy. Guess my contribution to the...

www.trawlerforum.com

Ted

 

[ranger58sb]

Thanks for the pointer, Ted!

Where the keel blocks and jack stands are will be painted next week after the rest of the paint has hardened. There were 4 thin coats of barrier paint that were rolled on in alternating colors followed by to coats of bottom paint. If rolled on, barrier coat takes more layers to achieve the manufacturers recommended mil thickness. Alternating colors makes it easy to ensure you haven’t missed a spot. After the boat is repositioned the process will be repeated in the missed areas.

I like it, great tip!

I wish I could say I was doing the topsides too, 'cause the hull came to me in pretty beat-up condition... but I'll have to keep thinking about whether I could ever (should ever) try to afford that too.

-Chris

 

[psneeld]

I agree with Ted as that was suggested here and there and I did the same.

I also followed the recommended time to first bottom paint application for superior adhesion and I used an eroding bottom paint of a different color than the final color.

Changing color coats makes it easy to tell coverage and wear...worked for me for most of a decade.

Boomerang (Shawn) reported no blisters when he owned the boat.

 

[Cigatoo]

Maybe a little off topic but......If repairing open thru hull holes with epoxy and glass no need to barrier coat over the repair? Correct? Or an I missing something?
The rest of the hull has 4 coats of barrier coat.

 

[rslifkin]

Maybe a little off topic but......If repairing open thru hull holes with epoxy and glass no need to barrier coat over the repair? Correct? Or an I missing something?
The rest of the hull has 4 coats of barrier coat.

I'd probably throw a coat over the repair. Shouldn't be necessary from a blister prevention perspective, but it'll give a consistent primer / surface to paint over.

 

[ranger58sb]

I agree with Ted as that was suggested here and there and I did the same.

I also followed the recommended time to first bottom paint application for superior adhesion and I used an eroding bottom paint of a different color than the final color.

Changing color coats makes it easy to tell coverage and wear...worked for me for most of a decade.

I've done the color thing with bottom paints, but hadn't thought far enough ahead to have that in mind for the barrier coats too. Sounds good to me.

In another (owner's) forum, I also saw a suggestion about hard-coat bottom paint covered by ablative. Hadn't thought of that before either, and we've not been using an ablative these last four years. Have to eventually give that some thought, too. Maybe even multiple colors for that, not just blue under black as we've done so far. Maybe...

-Chris

 

[Frosty]

As mentioned above, check the thickness required for a barrier coat. It's probably changed by now, but as I remember it (just as an example since I would imagine the concept holds), for Interlux it was around 2 coats for a "tie coat" (with overcoating at prescribed intervals to get the chemical tie) and 5 coats for a barrier coat (actually goes by millage but coats are a general guideline).

And yet I saw many boats when I was boat shopping that advertised they had a "barrier coat" but when I inquired further it was only 2 coats....

 

[psneeld]

From Interlux guide....

"Average expected coverage of InterProtect 2000E is 60 sq. ft.
per gallon kit when brushing or rolling and 45 sq ft per gallon kit when spraying to achieve 10 mils of dry finished coating."

I had always heard that you estimated sq ft of bottom and used volume to get coverage.

 

[Gdavid]

From Interlux guide....

"Average expected coverage of InterProtect 2000E is 60 sq. ft.
per gallon kit when brushing or rolling and 45 sq ft per gallon kit when spraying to achieve 10 mils of dry finished coating."

I had always heard that you estimated sq ft of bottom and used volume to get coverage.

I believe this guidance is including all required coats, simplifying the calculation. Calculating volume at such a thin height calls for odd units and any thinners in the epoxy that evaporate further confuses matters.

 

[psneeld]

I believe this guidance is including all required coats, simplifying the calculation. Calculating volume at such a thin height calls for odd units and any thinners in the epoxy that evaporate further confuses matters.

Just stating that I heard to use all the estimated containers needed for sq footage, not just stopping at the suggested number of coats in case they went on too thin.

 

[Gdavid]

That makes sense, I misunderstood your last sentence.

 

[Carriem1102]

We used multiple coats of Interprotect 2000. A tip is to buy both grey and white so you can alternate coats to ensure excellent complete coverage coat by coat. Also buy top quality lint free rollers designed for epoxy products or you will get bits in your paint layers. Read the instructions carefully so you apply the bottom paint within the window recommended for adhesion.

 

[Bacchus]

+1 for Introprotect. I did 3 coats before 1st bottom paint on our 1st boat. Reapplication window in importantvandvrequires planning to get 3-4 barrier plus 1st coat of bottom paintbwithin the time/ temp window. Miss one and you should sand th roughed and add another coat. I did 2 coats / day in mild V spring temps... 1 AM one PM repeat the next day. I also re blocked and did the support areas to coverv100%. Performance was excellent and no reappearance of blisters.
I did spot / area barrier after grinding / filling on current boat... no reappearance after 12 seasons so far.