primer for one-component paints over epoxy?

[Charles Neuman]

Any recommendations for primers/undercoaters to use for one-component paints, over epoxy? It's a small boat to be dry-sailed, so I am using topside paint all over.

I am considering using Epifanes' Monourethane or Pettit's Easypoxy paint.

Epifanes says their monourethane paint is NOT compatible with epoxy. Thus, you need to user their Interim undercoater to make it work. My only concern with that is that it says not to sand the undercoater (maybe because they don't want you to sand through and expose epoxy?). How can you have an undercoater that you can't sand? What if there is a run or something? Anyone use this product?

Pettit gives you tons of options but provides little information:

Here are some options for Pettit undercoaters:
6165 YACHT WHITE UNDERCOATER
6148 HI-BUILD BRUSH UNDERCOATER
6149 EASYPOXY WHITE UNDERCOATER
The first two are designed for wood. Can they be used over epoxy?
The last one is designed for surfaces that are not smooth. So if I can fair my hull properly and sand it smooth, I shouldn't need that, I suppose.

But wait, there are more options:
A store recommended
Pettit Protect 4700/4701
which is a two-part epoxy coating designed to prevent blisters. Seems like overkill for a dry-sailed boat, and it requires three coats, which seems like a pain.

Another option is:
Tie Coat Primer 6627
Pettit says it makes pretty much anything adhere to anything else. Maybe that's the safest bet.

I want something that's easy to sand, and of course that works with epoxy and with the paint. Any suggestions?

Thanks,
Charles

[BillyBudd]

Here's how I solved your dilemma. I took two small samples (3"x4" +-) of my hull material (1/2" ply) with epoxy on it and mailed them to Kirby paint. George painted them -- one with only topside paint and with primer+ the paint. Then, since I was passing by, I looked at the samples that he'd done and I agreed with George's thoughts when I phoned him...why bother with the primer as the topside paint adhered just fine? But will your paint company do that for you? Check out Kirby paint, call George or Bill and see what gives. The website www.kirbypaint.com will get you started with Kirby Paint. If you're stuck on your paint choice I suppose you can paint a sample, blowdry with a heat gun and watch for peeling?

[Charles Neuman]

Wow, that's some service.

I read in another post, and it was also just pointed out to me by someone else, that epoxy can act as a primer.

I could always test it, but here's a problem.... I read that adhesion problems often don't show up for a long time (months, years?).

I'm sure the paint companies have thought about this and have spent the time to test (or maybe I'm too optimistic). Epifanes has done their homework and is nice enough to report the answer: The monurethane is not compatible with epoxy.

Thanks for the tip on Kirby.

Charles

[Frank Wentzel]

Most likely Epifane's is just being very cautious. The epoxy adherance problem is caused by amine blush. That is the greasy film that forms on the surface of some epoxies, especially in humid conditions. If this film is removed (with water and maybe a little detergent) and the surface sanded, you will have excellent adhesion. Note that trying to remove amine blush with solvents will most likely not work. I know from personal experience that paint thinner won't work.

/// Frank ///

[Charles Neuman]

I should call them. If I am using amine-free epoxy, then maybe I wouldn't have that problem.

[Varna]

Charles,

I have had no problems using Pettit Easypoxy directly over WestSys, no primer- as suggested in Gougeon Bros on Boat Construction. I have had this book since '79 and perhaps now they recommend primers in newer editions.

Regarding Kirby's I understand it to be a soft enamel for wood app's and not ideal for epoxy/fg sheathed hulls. I have some Kirby's I plan to use on small glued lap hulls which will not be epoxy coated, but have yet to use it.

Here's what I have used over a few boats, and maybe you already know all this- I have followed the Gougeon advise in the book, which is clean FULLY cured (2 weeks min in my belief) sanded surface with hot water with trace ammonia and clean cotton- I use painters white rags from the paint store- and change frequently.

Next wipe dry with more CLEAN rags. Then Solvent wash with more CLEAN rags- wet wash so the surface shows wet-I prefer acetone. Change rags often if your working a big area. The idea is to use a rag to pick up the junk, folding over to clean rag after a pass or two. Once it is saturated discard so you aren't then spreading the residues around.

Then tack-rag off the surface at paint time- again opening and refolding the rag several times . Do all this right before the paint job so you control the situation- no chance for something mysterious to happen in a week span before paint.

I'll add that I like Pettit product all-around. Easypoxy cures very hard and sands nicely later for repainting etc. I did prime once on one boat just for the heck of it, following the painter instinct which says you must prime-Interlux primer because store did not have Pettit, before the Easypoxy. That worked fine, but 50% sanded away since the film is so thin- a waste of time and material I think. At least with the PolyU Enamel you start right off with a thick film and thus a second coat goes over something of substance. Some may disagree, but you have to sand irregardless of primer or topcoat material anyway, so why not just use the heavy stuff. And the FULLY CURED epoxy IS the primer in spades regarding film thickness.

Also I wash with the ammonia solution really well after a FULL cure period BEFORE doing any sanding so I am not possibly sanding in the waxy amine- this I have wondered about regards some contamination issues reported- not waiting long enough for the amines to fully surface before clean/sand. I am referring here to the final epoxy coats on a coated or F/G sheathed hull which is now ready for the final finish sanding after all the fairing is done and a couple of epoxy top coats have been applied.

The key to good paint jobs is to be clean and sterile before the paint goes on, and in my experience with epoxy a long and full cure period before the final cleaning/sanding/cleaning/painting sequence. This has worked well for me on the boats I have personally built.

[pipefitter]

No primer here. I used a cheap primer to read the hull for not being able to detect fairness due to the dark colored wood but I sanded it all off,circled the lows and highs and repaired them with the epoxy it was initially sealed with.

Right after paint.
http://home.earthlink.net/~tigmaster41/sitebuildercontent/sitebuilderpictures/img_2259.jpg

Two years later
http://home.earthlink.net/~tigmaster41/sitebuildercontent/sitebuilderpictures/p3200053.jpg

[water break]

I would probably stay away from the Pettit 4700/4701. I had planned to prime my boat with it and tried some small areas. It is very difficult to apply evenly and sands like stone. I will use it on the bottom where it will be covered with antifouling and looks are not important.

[pipefitter]

That Kilz primer is some pretty good stuff. It's a sealer as well which is great when things such as amines might be floating around. If I was going to prime for an alkyd system,that's what I would use. It seals in things like smoke damage,nicotine,kitchen film from cooking,water stains. All things that commonly bleed through topcoats on other alkyd or water based paints for other apps. It sticks very well too.

[mike hanyi]

in raid finland I have seen twice major peeling because of the racing decal being removed.

now where is Richard Wynn when we need him....
he was at sail caledonia and afterward the race decal was removed from his strip/epoxy boat, it ripped off everything back to the epoxy
he asked me about our decals up front, I said they are thin shelf paper material and come easily off... well same thing happened and ruined his nice sprayed hull. I asked some questions and Hempel/Blakes paint said that if it is ripping off paint and primer then it was because the hull was not sanded well enough as epoxy is very very hard and needs sanding with max 120 grit very well for anything to stick well to it.

plus that epoxy needs to be dry which may take months to kick, thats why 2 componant primer is a good practice.

mike

[Todd Bradshaw]

I believe I've done six sailboats with either Easypoxy or Brightside over sanded epoxy with no primer and a bunch of clear-finished strippers with varnish over epoxy and obviously no primer and have yet to have any kind of peeling, flaking, etc. The only deterioration I've seen was from U.V. - which doesn't care whether a surface is primed or not. I even have a small alcove on my garage wall that's Brightside on WEST-coated plywood and about five years old and it's out all day, every day.

I look at primer as nothing more than a very fine fairing compound for situations where you're trying to hide small surface imperfections and as yet I've seen no evidence that it improves the bond or the finish on properly prepared epoxy surfaces.

[pipefitter]

Another thing folks should realize is the difference in choosing abrasives. On power sanding equipment,the grit count soon becomes higher just by adding electricity or air to the tool. 80 will become 120 in short order where it will act more like 80 when done by hand.

[willmarsh3]

I used Brightside on a rudder that I built and glassed with WEST epoxy. The paint did not cure. I had to wipe the whole mess off with acetone and start over. My experience is probably different from Todd's in that this was new, just cured epoxy and at that point I did not know about the amine blush.

I have since used the Interlux 1 part precoat primer followed by Brightside with success.

[Todd Bradshaw]

Yes, you do have to remove the blush, though I'm continually amazed by the fear that many boatbuilders have of amine blush (many of whom seem to have no actual experience in dealing with it and appear to simply be spreading information that they read somewhere else). A few minutes with nothing more than a Scotchbrite pad, a bucket of water and a roll of paper towels will remove it without a problem. I figure that it's probably wise to treat every epoxy surface that way before sanding or top-coating it, whether they claim the resin blushes or not. One way or another, there may well be something that formed or settled on the surface that you would rather remove than spread around or overcoat.

I'm a pretty loyal WEST Epoxy user and have been for many years. I'm comfortable with the products and procedures and I appreciate all the work and testing that the Gougeons and their staff have done over the years to pioneer the materials and techniques involved, so I support them. It holds most of the vital parts of my iceboat together, as it does most of them around here, and at those speeds glue failure is not an attractive option. Blush removal is just a part of the process, and a fairly minor one in terms of time and effort required, but it is an important step. Once you have achieved a properly cured, properly cleaned and properly sanded epoxy surface, it seems to make a pretty darned good base for painting (better than most pieces of wood, for example) and most primers don't contain and kind of magical ingredients which would make them stick, dry, cure, harden, or resist the elements, expansion, contraction etc. any better than the paint itself does. If you sand badly, primer will give you one more chance to get things right before the paint goes on, but if there is anything left on the surface that would inhibit the adhesion of enamel (blush or any other form of contamination) expecting primer to make everything peachy and hold things together is pretty poor logic.

[pipefitter]

Even on plain wood,the longer drying topcoats soak into the wood better than the faster drying flat primer does. It will all but disappear on open wood for a couple coats. Most production operations can't really afford the extra time and coats and the primer becomes a color blocker so that less coats of the more expensive paints are used for better color coverage. I cleaned the epoxy with the water as suggested and right before paint,I used rags soaked with mineral spirits to wipe it down one more time. Nothing transferred to the rags so I figured I was good to go. Whenever I hear of paint not drying or falling off,I know what has happened pretty much. I did some spot repairs where I put the bow eye in after the fact and such and when I sanded the surrounding area to add some glass and epoxy,the paint that was there sanded to a fine feather edge. If paint/primer is not adhered,it will not feather.