alkyd enamel paint over epoxy

T

teq56

Here's a question. Bought a project car that was painted in epoxy primer and then he spayed a coat of cheap alkyd enamel paint directly over the epoxy. He said we just wanted a cheap color coat so he could drive the car and sell it. Now I have it and want to do it right... but wondering if I need to just sand it and shoot single stage or go all the way back to epoxy and/or bare metal. Every thing under the epoxy was done right and is sticking just find.... most of it would be sanded off before I top coat but in some low lying areas there might be some old enamel left. I would say 95% (or more) of it will be sanded off before I sprayed single stage on top. I'm just a hobbyist so want to know how to do it right. If there is a little alkyd enamel in low areas is that a problem?

Thomas
 
I know people that clear over that stuff after it's cured a few days... There are WAY better experts on this site but SPI clears tech-sheets say it can go over 'activated' Acrylic Enamel, I don't think 'cured' Synthetic Enamel would be so very different. Good luck !
 
If just a daily driver and the alkyd enamel had a hardner added to if it was mine I would sand all off that I could and epoxy and then paint. If something I cared about and wanted to keep I would start over from bare metal, epoxy and paint. I have painted a many of gallon of alkyd enamel on horse carriages but that was on wood I personally wouldn't use it on a car that I was going to keep.
 
Alkyd enamel is an architectural or industrial coating. It is not usually catalyzed it is air drying single component. I am also skeptical about the paint work prior to the enamel. Why would somebody go through all the steps correctly and then cut corners on the last step ,then sell it gas monkey style. Whats done is done. My opinion would be to mechanically strip it to bare metal, d.a. ,scotchbrite roloc, 3m roloc bristles, 80 grit sandpaper. Point being your paint job is only as good as your foundation. Why spend good money and time on quality products like spi if you dont do all the steps correctly. I think everyone here has been in similar dilemmas but your time, patience, and persistence will be rewarded .
 
I knew the car before... he did nothing but sandblast, epoxy prime. Not fill, no bondo, nothing. The alkyd enamel was catalyzed as well. It would only be left in very few low areas. 99% will be sanded off.
 
Maybe check some of the areas for solvent resistance, lacquer thinner,acetone,urethane reducer, see if there is any paint softening. Then go from there as long as you know that the sandblasted metal was also prepped properly. Then spi epoxy test area and look for any issues,adhesion (let epoxy cure 24hrs min firmly place 2" wde tape over area, cut x through with razor and peel tape, tape should have very little if any epoxy on it)then look for any other issues such as wrinkling and softening.
 
Alkyd enamel isn't activated, it crosslinks using oxygen from the air, much the same as drying oils like linseed oil. If the paint put on the vehicle actually had a catalyst, it was most likely acrylic enamel, which in theory is OK to prime over.
 
I used to paint horse carriages with alkyd enamel and some companies make a catylyst for their paint or I would use synthetic enamel hardener. After five or six years they still shined good but that is on wood and kept in a shed more than in the sun, I wouldn't want it on my car but I wouldn't be caught wearing a pink shirt either, but I got plenty of friends that wear them. Depends on how much you want to put in it, I used to think it was pretty good paint back before I knew any better, now I'm sticking with spi just wish they made more colors!
 
If it was catalyzed, at this point it would be stable enough where if 90% was sanded off, you should be fine.
If it was not catalyzed, it will sand gummy and anything you put over it will wrinkle, even epoxy attach it.

If it has had,s ay 6 months of sun and catalyzed, it could just be scuffed and a coat of epoxy as a barrier coat and you could go from there.

With all that said, take off what you can, to be safe.
 
shine;27538 said:
lay a rag soaked with thinner on it. this will tell you all you need to know.
Click to expand...

That's what I would do.......cept really I would strip it period
 
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