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Discussion Starter · #1 ·
I posted a question on the Interlux forum (yachtpaint.com) on how to apply micron extra (ablative bottom paint) on to freshly applied West System epoxy (still "hot" or tacky but not fully cured) epoxy. The response was to treat it just like cured epoxy: wait for full cure (3 - 7 days), apply Interprotect 2000e, and then apply micron while Interprotect is thumbprint tacky.

That just doesn't seem right to me. I had always heard that bottom paints adhered best when applied hot, but I didn't think it mattered whether it was West System epoxy or Interlux's Interprotect epoxy..

I wonder if this is just the corporate CYA response and not entirely grounded in practicality?

What do you guys think?

Here's to hoping Fastbttms joins this thread..:D

One more bottom paint question: What is the best way to prep old ablative for a new and different type of ablative bottom paint ? Interlux will say to sand with 80 grit, wipe with special thinner 216, apply 1 coat of primocon, then bottom paint..but I want to hear what experience you have or methods you guys are familiar with. (I was thinking of sanding, wiping with xylene, and then applying bottom.)

Thanks as always!
 

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I 'used to' hot coat (interlux) bottom paint to freshly applied epoxy barrier coats, etc. Eventually the ablative bottom coat will fail AT the interface between the barrier and the first layer of old bottom paint and the failure will be loss of adhesion and huge FLAKES of missing bottom paint.

My chemical knowledge, and in spite of Interlux recommendations, now leads me to: let the barrier fully cure for several days, then wash/scrub with HOT water and soap to remove any possibility of 'amine blush', let cure some more, wash again with HOT water after sanding with 80 grit ...... and then apply the new bottom paint. I find this lasts much longer and I dont seem to have the frequency of bottom paint adhesion failures of the initial bottom paint layers.
 

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My advice is to follow the Interlux rep's advice. They aren't in the business of steering you wrong.
 

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Unless you have a degree in coatings, and have specific knowledge of this paint, I would assume that the advice from interlux is far superior to any Internet forum advice. They spend millions in R&D to test how to apply it. Even a regular bottom painter isn't going to have their level of expertise.
 

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I made the mistake of not putting the bottom paint on right after the barrier coat of 200E Now the bottom paint is not well adhered to the epoxy.. but it's not a terrible thing. Hindsight means more work since cured 200E would need to be sanded to give bottom paint better adhesion.
 

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If you still have your arms attached after prepping the bottom for an Interprotect job, go over it again, after cure, with 80 grit on one of these sanding boards. It will give you a very fair bottom, ready for paint. I've never had a flaking problem doing it that way.

Optionally, you can use the board BEFORE the coats of Interprotect and hot coat the bottom paint but you end up with whatever surface was left after rolling on the Interprotect.
 

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Discussion Starter · #7 ·
Ok, I'll follow the Interlux advice. I was really hoping to have the project done in a day - both blister repair and bottom paint touch-up all tidied up.

With these temperatures the epoxy will need a week before I can apply 2000e. Better to do it right I suppose..

Thanks all!
 

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Your epoxy has to be fully cured and deblushed before antifouling can be applied. Ideally, Interprotect would be the "finish" barrier coat between the West (asuming it was applied to fair and fill imperfections in the hull) and the bottom paint. The idea behind rolling Interprotect epoxy paint over the west epoxy is that it provides a completely uniform surface for the bottom paints to chemically bond to, and seals the underlying epoxy. then apply your ablative while the barrier coat is tacky.
 

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Discussion Starter · #9 ·
The idea behind rolling Interprotect epoxy paint over the west epoxy is that it provides a completely uniform surface for the bottom paints to chemically bond to, and seals the underlying epoxy. then apply your ablative while the barrier coat is tacky.
That's exactly what doesn't compute to me. West epoxy doesn't need a sealant. West epoxy IS a barrier coat. I don't understand the difference between (a) applying ablative to a tacky Interlux barrier coat or (b) applying ablative to a tacky West System barrier coat. I'm not saying you are wrong - I just might be thick headed! :eek:

I thought the amine blush only forms well after the tacky stage, into the final cure stage and when exposed to air, especially humid air. To my (admittedly non-chemist) brain, it seems that if the west is coated with bottom paint while still tacky, then 1) no amine blush will form since it is cut off from air, and (2) the west system might chemically link somewhat to the bottom paint?

Perhaps the difference is that the 2000e is a COMPLETELY non-blushing formula of epoxy and that's why it is better suited for the bottom paint?
 

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Okay, I am a little confused. If you have added a thickener like colloidal silica to the epoxy to use if for filling blisters and fairing, it needs a coat of unthickened epoxy as a barrier coat and that epoxy has to cure.


From West's own site:
WEST SYSTEM | Use Guides - Barrier Coating

"Apply a minimum of two coats of WEST SYSTEM epoxy for an effective moisture barrier. Apply three coats if sanding is to be carried out. Moisture protection will increase with additional coats and, in the case of osmosis repair and protection, six coats or about a thickness of 600 microns must be applied. Six coats, with 422 Barrier Coat Additive™ in the final five coats, provides maximum moisture protection. Additives or pigments should not be added to the first coat. Do not add thinners or solvents to WEST SYSTEM epoxy."

"Apply second and subsequent coats of epoxy following the same procedures. Ensure the previous coat is still tacky, but has cured firmly enough to support the weight of the next coat. To avoid sanding between coats, apply all coats in the same day. After the final coat has cured overnight, wash with clean water and abrade the surface to prepare for the final finish."


So either way, over the repair epoxy, you need to roll on a barrier coat x 6, and west reccommends an additive. I like using interprotect because I KNOW it is compatible with West Epoxy, and I KNOW it is compatible with the Interlux anti-fouling paint i am using.
 
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