Is any epoxy paint a good epoxy paint?

[SVTatia]

Here is a question for the paint specialists out there:

I will be applying a barrier coat on my Allied Luders 33 and would like to know what are the differences if any among PAINT manufacturers.

Other than the popular marine suppliers such as International, US Paints, Petit, etc there are others with household names such as Sherwin Williams and Benjamin Moore that cost quite a bit less.

If a two-part epoxy paint contains high-solids and is recommended for immersion in fresh and salt water would that automatically classify as good for barrier coating? Does the mixing ratio matter?

I'll appreciate you feedback.

[tommays]

There is magic stuff they add that is supposed to stop water osmosis

Normal epoxy paint like Awlgrip 545 is not supposed to be a good barrier coat

For example West sells a 422 powder that you mix with epoxy to turn it into barrier coat

[mitiempo]

Epoxy paints are not good barrier coatings. Proper barrier coatings like International's Interprotect are not paints but coatings with a specific design purpose. 5 coats are required for proper protection, and the hull must be dry which takes several months to achieve.

To my knowledge neither Benjamin Moore or Sherwin Williams make marine barrier coatings - I don't think they make marine paints at all.

When barrier coating you want the best protection available, not the least expensive. You are trying to seal the inner layers of the hull structure from moisture which the gelcoat and polyester resin cannot do.

[SVTatia]

That is precisely my question: What is the difference bt the "designed marine barrier coatings" and the other high-solids epoxies made to be submersible.
If the brochure says marine, is this an automatic qualifier? I am not trying to be be cheap, just avoiding paying for a "marine" label when I dont'have to.

[tommays]

A barrier coat has platelets for lack of a better word In the mix

It's not like you have to do anything and many will argue it will often fail to work

Neither of my 1981 J24 hulls ever had anything used and never had issues BUT were never in the water more than 6 months at a time

I know of many J24 hulls kept in warm water year round that have had pretty bad problems

My 1970 Cal 29 has no issues But had a really good barrier job done and I am sure going to insure it stays in good shape

[mitiempo]

The true epoxies, not epoxy paints, are the only products that are unlikely to allow water transfer to the structure of a fiberglass hull.
If the coating is not more of a "barrier" to moisture than the original polyester based gelcoat why bother?

[Maine Sail]

Epoxy "paint" and epoxy "barrier coat" are two different products. There is a reason most professionals I know choose Interprotect. My boat yard has tried every barrier coat to come down the pike to save money but they always come right back to Interprotect.

There are literally hundreds of different ways to formulate epoxy and the ones specific to barrier coating are designed specifically for this. All the epoxy makers also have additives you can add to their epoxy to make them a barrier coat. I have used West System, Pettit, Interprotect and MAS. The Interprotect is the one I prefer by quite a long shot and I find it well worth the money IF you install it correctly. Many people don't apply barrier coats properly and essentially waste their money. The hull has to be dry and 100% free of all old paint before coating. The final layer and hot-coating the bottom paint is the most critical step and many folks really mess this one up...

With ANY of them follow the directions...

[fallard]

I've used Interprotect on fiberglass hulls as well as steel and aluminum underwater structures (e.g., centerboard, OB bracket) with excellent results. The key, as Main Sail said, is preparation and following directions, particularly on recoat times.

[SVTatia]

Thank you all, and you Maine Sail for sharing whats being used and worked - nothing beats empirical evidence.
Interprotect will be my choice.