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Old 01-07-2012, 08:30 PM
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Primer to EP adhesion problems

Sprayed Napa Epoxy primer over bare metal valve cover 2 days ago. Sprayed 3 coats of Omni AU primer today, Used wax and grease remover before EP and primer. Used Gray scotch bright before high build primer. The primer went on extremely dry and it was difficult to get it to lay on wet. Adjusted the air pressure but no change. Half an hour after spraying, it just peels off in little sheets! Should I have sanded EP with 320 before primer? Any advice?

-Tom

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Old 01-08-2012, 12:34 AM
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My guess is the primer was not compatible with epoxy, etc. maybe metal was too cold, not right hardener, etc. Really need more info about each primer.
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Old 01-08-2012, 08:47 AM
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I think the epoxy needed to be scuffed, but that is only a hunch.
The 2k primer should have went on wet. Too dry and very likely it wouldnt stick to well .
Read the data sheets that came with the paint .

Last edited by Old Fool; 01-08-2012 at 08:53 AM.
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Old 01-08-2012, 08:56 AM
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the epoxy primer cured in those two days you let it sit. You should have sanded it then applied your finishes. Most auto epoxy primer is designed to be painted over fairly quickly. or you let it cured and sand the imperfections and then paint
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Old 01-08-2012, 01:13 PM
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I know there can be problems with two different paint brands. I used DP 90 with the omni primer in the past with no problems, but this time I used Napa EP. I sanded the EP with 320 maybe too smooth.Sat for those 2 days and scotch brite wasen't enough?I could not get the primer to go on wet, the primer seemed kinda thick , Maybe I need to thin it down.The EP sprayed just fine with the same gun.I've got the primer stipped back off it now,and the EP sanded more aggresively. The shop is well heated. Thanks for all the input. Tom
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Old 01-08-2012, 01:33 PM
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primer

i had the same problem with the dupont nason full cryl paint i bought from dupont. the manager with 38 years experience told me that epoxy primer adheres to anything and stops rust very well. the part i didnt hear the first time was "spray your base coat 1 hour after the primer dries" so basically spray your primer, wait one hour, then spray your paint. the lady insisted you do NOT have to sand epoxy primer if you follow these instructions. if you wait till the epoxy is fully cured the surface tension of the epoxy has made an effective seal against the outside elements which is why its considered primer sealer and a very good rust preventative. unfortunately i'm pretty sure thats also why you have adhesion problems cuz i had the same thing happen with my acrylic top coat. good luck sir
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Old 01-08-2012, 02:54 PM
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So maybe sanding the EP isn't enough I'll have to spray a coat of the EP right before I prime. I'll check with the Rep before I spray anything else. Thanks
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Old 01-08-2012, 05:53 PM
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Next time do yourself a favor and use SPI epoxy. Price is great and the prodct is better than great. You can spray most any brand of anything on it, but I suggest using SPI 2K primers too. Great product and a good price.

Oh, you cannot beat the customer service Barry provides.


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Old 01-08-2012, 08:44 PM
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sand everything very completely. I mean sand until you think you are done and then sand some more. re prime with epoxy primer,wait until it flashes completely 45 min to an hour. then put your finish on. You will probably have to clear shortly after if you are using base, clear system. if the primer seems dry then thin it down. do this in increments. you dont wont any runs

the reason you do everything so quickly is that all your layers of paint "bite" into each other when done this way. if the materials cure too much then they dont "bite" into each other
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Old 01-10-2012, 10:54 AM
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Sprayed another part with primer that had been EP'd the same time as the other. This time I could tell the primer was way thinner,and it went on wet. Maybe I mixed the primer wrong the first time.Thanks for the help. Tom
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Old 01-11-2012, 08:11 PM
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It might also be because some epoxies have a "blush" on them when cured. This is removed easily with hot, soapy water.
Others have already pointed out that if you get your paint on quickly enough, the blush hasn't had time to develop.
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Old 01-12-2012, 09:02 AM
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I don't believe you are supposed to sand epoxy primer in general since it does not sand well. At least with the Omni epoxy primer i've used that is the case. I would still scuff it if i were spraying over it but as for sanding it down like your average primer i don't believe its made for that. They say epoxy primer has some of the hardest stick in the industry and is very good at holding down rust but like i said the Omni version was not made to sand like your average primer. I'm not sure about the brand you use. Assuming you prepped correctly like wiping off the prep solv with a new towel, mixed the activator to the primer that is peeling since you did say it was thick(you can actually use a little reducer to thin it out some, believe its 10%, or just put in a little bit more activator to thin it out, then it could be just a bad batch of chemicals which does happen. Only other thing i've seen where it peels out like you're describing is from poorly stirring or shaking the mixes, or just not putting in the proper amount of activator. I just doubt its a primer on primer issue....
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Old 01-12-2012, 12:19 PM
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Omni paint line is ....crap. I mean it's super cheap line of PPG. If you have ShopLine I would suggest you use it over Omni. Just don't expect great results when you're using low end paint products, it's just gonna happen.
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Old 01-13-2012, 07:57 AM
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Quote:
Originally Posted by mitmaks
Omni paint line is ....crap. I mean it's super cheap line of PPG. If you have ShopLine I would suggest you use it over Omni. Just don't expect great results when you're using low end paint products, it's just gonna happen.

i used to spray Deltron2k only for years and years, and before that Dupont Chromobase... and for about the last year~ or so i've tried Omni or Omni plus lines and job end results aren't much different for the most part. The biggest difference being Omni mixes need to be played with to get the color match blendable much more often because they really don't have anywhere near the color match system or variety the higher paint lines do.

I mean i have a Deltron2k system but haven't used it much lately due to ordering out premixed Omni that is doing the job fine for the most part with some tinting....
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