2-part epoxy paint over 2-part poly?

[Stargazer14]

question for those of you with paint experience..

I painted my cabintop(glassed ply) with an Interlux 2 part polyurethane, and of course, due to that whole thing with the tide being right, the stars lined up perfectly, and assorted estrogen cycles, it didnt come out as sweet as I would have hoped. In fact, I'd like to re-do it.
So, having two gallons of part A and part B of a very nice Epoxy paint I have used on concrete floors(it even sez 'for marine use' on the label!), I'd like to re-do the top with this stuff. Did not find any writing about what my question is:
The question - after a little cleaning, can this epoxy be put over the poly with out too much trouble?

[Allen Foote]

First off, why did the previous paint fail? Does it have anything to do with the surface prep before painting? Or was it applied too thick? And define "a little cleaning".

The only problems with incompatable paint has to do with the drying agents and/or solvents attacking the previously used paint and "lifting" it off. If you have good adhesion...go for it....and let us know if it works.

[ 01-21-2004, 04:46 PM: Message edited by: Allen Foote ]

[Wild Wassa]

This is a very interesting question, Skipper.

Generally epoxy will stick to most surfaces. With poly I find, when I cut it back, I need to apply the next surface within a day. The poly that I use Aquacote, has a surface that goes glossy, a few days after sanding. I'd probably put a coat of epoxy on the heavily sanded poly then the epoxy paint over the epoxy. I'd key the scratch to around 280 grit, for the epoxy coat, and no finer than 320 grit for the epoxy paint. I'd try to take as much of the poly off, by sanding, berfore applying the epoxy. Maybe 400 grit for the top coat. I'd most likely wood, if the poly surface was bad, if it's just ugly, cut back heavily.

That's if I didn't have to ask the paint manufacturer. There are also sandable epoxy undercoats, that one could consider using.

Warren.

[JimD]

Not an answer but a little grist for the mill, isocyante cured two part poly's cling to epoxy/fiberglass wonderfully. They shouldn't be used over ordinary one part paints, though. I used a regular marine paint (Pacific Sailor) over 2part plu and it stuck just fine although once when the boat took a good bashing against a wharf when a strong wind came up suddenly the Pacific Sailor scraped off the hull but the poly underneath held up.

[Stargazer14]

Just for the record, the 2-part poly was put on according to manuf. directions, only after the
glassed cabintop was washed for blush, then prepped with recommended solvent cleaners.
The poly was not put on too thick, in fact if anything, it could have been thicker or more coats applied. In the end, the look was not even - some parts glossy, some matte.
Perhaps i will just give it a good sand in the spring, tack any dust off with a prep solvent, and epoxy paint away.
I'll dig up this thread in late April and let you know how it worked out.

[Scott Rosen]

A couple of years ago, I had this discussion with one of the tech guys at Sterling/Detco, which makes both LPU and epoxy products. He said that LPU (2 part poly) sticks great to cured epoxy. But the opposite is not true. Epoxy does not adhere well to cured LPU. Go figure.

[Stargazer14]

Oh well now thats just great.

So maybe I'll sand a little more..... :rolleyes:

[Buddy]

Epoxy paint doesn't have anywhere near the UV imunity of LPU. Interthane Plus is like all LPU's a very thin film. Really should have a thick primer, preferably epoxy, to seal upa nd surface flat all the imperfections it's going to reveal. Why are you not considering sanding and applying more layers of the Intertahne Plus at this point? Because you have the other paint/. I would recommend staying with this topcoat, consider what you have on as an expensive, thin primer coat, and press on. The LPU will really be more weather proof and harder to scratch and scuff than an epoxy topcoat.Better in the long run.

[Stargazer14]

You have brought up some good points, I did not even think of the UV hold up.
The main reasons I was going to go with the epoxy is; 1) I didnt like the way the LPU turned out for as expensive as it was, and 2), I have about 2 gallons of this white hi-gloss epoxy sitting here, cost - nothing.
But, if i have to dig into my daughters lunch fund again to get a good looking cabintop, well, then so be it. Little girls love their dads, she'll understand. Thanks for the info guys.

[Wild Wassa]

Originally posted by Scott Rosen:
"<snip> ... said that LPU (2 part poly) sticks great to cured epoxy. But the opposite is not true. Epoxy does not adhere well to cured LPU."

Scott, I'd like a definition of 'well', Sir.

I find the opposite to be true, Sir. My only experience of well cured poly though, is about a month of curing for the poly, except for one dinghy's poly which was old over a decade I'd say. I fair with epoxy and macros, between the layers of poly paint when needed. Mostly the poly coats are about 2 to 3 weeks old. If you are correct and 1 month is well cured, ... the ACT Sea Scouts boats should be loosing their skins by now. My oldest boat skin with epoxy over poly is just over two years since her new skin, she still looks fine.

I was going to do another epoxy over poly, tomorrow, this time the deed is on my boat. Tell me more please, if there is more to know?

Warren.

[ 01-30-2004, 01:34 AM: Message edited by: Wild Wassa ]

[Scott Rosen]

Warren,

I was just passing on the information that a chemist at Detco gave to me. I don't have any more information. Like you, I've used epoxy and microballoons to fair a surface painted with LPU. So far, no problem.

And please don't call me "sir." ;)

[Wild Wassa]

Cheers Scott. You threw a cat amongst my pigeons with the Detco advice, it made me asess what I was doing. Thanks for replying.

I've only just learnt to cope with the marine plastics, so changing what I think works would have created a great deal of stress, and probably a six dinghy recall.

Warren.