Am I going to lose my bottom paint

[cburger]

After two long exhausting years of performing a blister repair job it finally was time to apply barrier coat and bottom paint. As part of this job the gel coat was completely removed to expose bare glass.

Two coats of System 3 Clear coat epoxy was rolled on, second coat was applied while first coat was slightly tacky and the first coat of Petit Hydrocoat was rolled on when the final coat of epoxy was still tacky.

After the work was completed by chance I came upon System 3 instructions for using their epoxy as barrier coat that indicates 4 coats of epoxy minimum should be applied and that the final coat of epoxy should be dry and sanded
before applying bottom paint and that if this direction is not followed a
nd the bottom paint "Hot Coated" to the epoxy you risk having the bottom paint and epoxy fall off after the boat is launched.

The vessel will remain on the hard for many months before launch.

What are the chances that the coatings will actually fail?

[SalingSue]

What did the paint manufacturer tell you?


I’d talk to the people who made the stuff before some guy on the internet SGOTI

[Dsanduril]

It's not the sanding so much as the amine blush from curing:

Hose and sponge the hull with water to remove any oily surface film on the cured epoxy. This is a water-soluble film and will be thicker if you applied the coating in humid weather. It is a by-product of the epoxy curing reaction. Solvents do not remove this film.

If you hot coat there is no chance to remove the blush, and some may continue to form under the paint as the epoxy continues to cure.

Hot coating over epoxy paint primers is pretty typical/standard, but over an amine-cured structural epoxy (and both Silvertip and General Purpose are amine-cured) it can cause a lot of problems. Sorry, I would not be surprised to see paint failures.

[Chotu]

I think what you missed is the primer. You should have had a tie coat primer between the last layer of system three and the bottom paint.

Unfortunately it’s quite possible the paint won’t adhere. Especially if there was any blush.

Did you use system three Silvertip by any chance? Non blushing if I recall

[cburger]

My understanding is System 3 "Clear Coat" resins has no amines.

PRODUCT DESCRIPTION
Clear Coat is an extremely low viscosity, water white, "penetrating" epoxy system. Clear Coat cures to a brilliantly clear, very tough finish without the usual "amine blush" associated with some epoxy resin films. Clear Coat contains no volatile solvents.

A two part epoxy coating and laminating resin for use in marine and woodworking applications. Use as a sealer, topcoat, or saturation coat.

Features a convenient 2:1 mixing ratio.
A clear, almost water-white, solvent-free epoxy system.
Cures to a clear, glossy, blush-free surface.

[Thumbs Up]

I would be surprised if it didn't fail. A water based paint hot coated over epoxy is suspect. two coats of epoxy instead of the minimum of 4 is not good. You can test the adhesion with some packing tape but seeing as you need a better barrier coat anyway it seems like a redo is in order. Sorry.

[Dsanduril]

Yes, the Clear Coat is not an amine-cured resin. The instructions in the System Three Epoxy Book for barrier coats assume one layer of Clear Coat (to help penetrate/seal any exposed weave) and then four coats of standard epoxy to actually provide the barrier.

Apologies for missing the point that you had only used Clear Coat. I'd only be guessing, because I don't use that product that way, that you might be OK. However, after all of your hard work two coats of Clear Coat does not a true barrier make.

[cburger]

At this point my biggest concern is only applying two coats of Clear Coat. There had been info on this forum regarding how effective this resin has been as a barrier coat.

I will splash vessel and regroup at haul out time.

[S/V Illusion]

Originally Posted by cburger

At this point my biggest concern is only applying two coats of Clear Coat. There had been info on this forum regarding how effective this resin has been as a barrier coat.

I will splash vessel and regroup at haul out time.

As has been pointed out, you are asking a bunch of strangers with little if any experience and probably less knowledge to guess what might happen. Rather, why not ask the manufacturer who knows.

This reminds me of the financial advice questions some ask here on a boating web site. Wrong venue!

[Nicholson58]

Originally Posted by SalingSue

What did the paint manufacturer tell you?


I’d talk to the people who made the stuff before some guy on the internet SGOTI

I agree. I met with the Petit and Interlox tech reps before painting after a similar project like yours. They were both exceptionally helpful and they said the instructions on the cans were to be ignored regarding the transition to bottom paint. They gave me combined detailed instructions.

Get hold of technical assistance from the horses mouth.