to seal or not to seal?

S

swvalcon

I hope Barry has a answer for me. What I've been doing on my restoration jobs is as follows. Strip paint, do body work, some times epoxy frist all depends on what kind of body work needs to be done. Then I will epoxy good let dry overnight and scuff. Then 2-k prime untill all is blocked and ready for paint. At this point I will be sure everything is sanded good with 320-400, clean up good, Wax and grease clean and tack off. Put down at least two good wet coats of black epoxy and check while wet for any flaws or waves. Let dry as long as possible and if warm out I will park out in the hot sun to bake everything good. But here in MN sometimes it doesn't get very warm. At this point I will wet sand with 400 and go over it with a red scuff pad and if no bare metal areas are showing I will clean good, wax and grease, tack, seal and paint. Now some times all I do is paint at this point and skip the sealer. Will this skip come back to bite me or is this ok?
 
I feel that basecoat adheres very well to new applications of epoxy that are no more than a few days old very well without mandatory sealer. Long-term chip resistance using this method has been very good for me. Epoxy that is less than 72 hours old is pretty much as good as sealer in my book, but opinions vary.

Sealer is very important when painting over fully cured primers.

I just re-read your post, if you are trying to fully cure your final epoxy by putting outside, etc., you should use sealer. If you spray your final epoxy and leave it in the shop for a couple of days, then wet sand it and paint it, you are OK in my book.
 
shine;27548 said:
depends on what you want. mechanical adhesion or chemical adhesion . i seal everything.
Click to expand...

i with Shine i seal everything!
 
I know this is an older thread but thought I'd add a description of a problem I experienced that I think is related to choosing not to use sealer. I got set up this morning to spray SPI red base coat over a repair spot on a door panel shot the previous day with the same red SPI base. Although I'm still trying to forget the slow-motion nightmare of the damage incident, suffice it say that I had to take a freshly based panel and do a repair all the way back to bare metal.... I finished the repair with a 2 coats of SPI 2K primer and let it cure overnight. Then, this morning, thinking there wouldn't be much difference in the way the red base would cover the primer if I didn't seal it with reduced epoxy, I laid on the first coat of base (on the full door panel) and knew immediately something wasn't 'right.' The repaired, primered area seemed to soak up the color and barely showed any signs of hiding. On all previously painted panels, I've been sealing with reduced epoxy. I use 3 coats of spi red after the sealer to get excellent coverage. Today on the un-sealed repair, it took several more coats (and lots of time) to finally achieve hiding. While I'm not certain it was the lack of sealer causing the problem, it's the only thing I can think of that I've done differently. I won't make that mistake again -- wish I'd read Crashtech's and Hotbo's advice before I started.
 
not really sure whats goin on there. the ONLY time i have seen anything soak the color out of the paint resin is when using a candy. filler will suck the dye right out of the paint if there isnt enough primer sealing that. this is why on a candy job sealer is not an option. on regular basecoats though the color is an actual pigment not a dye so it cant migrate through layers with the solvents in the system. could it be that since you had 2 different colors there and the red just wasnt covering too well? was the red mixed well? pigments settle out in the can or mixing cup?
 
My guess is that when repairing a spot with the red, the transparency of the color becomes painfully apparent. When applying color over a uniform surface, lack of coverage does not seem so severe. The fact is that many red and yellow overall paint jobs, for example, do not have full coverage, making repair matching difficult. If the job being repaired does not have full coverage, even repairing with the exact paint used in the job will not result in a match, because the color blend area will then have more coverage than the rest of the vehicle.
 
Just getting back to the responses here. Thanks Jim C and Crashtech ... I appreciate the feedback. As a hobbyist, I don't paint daily so I haven't done any other tests. But when I fire up the red base again in a week or so, I'll try to find a test panel and spray sealer on 1/2 and leave the other in 2k. We'll see if there's a big difference like I experienced on the repair spots. Here's the door after some wet sanding and I'm happy enough with it ... repaired the lower left 1/4 of the panel.

Door In Paint.jpg

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