1K vs 2K epoxy primer second coat

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PostPosted: Sat Mar 20, 2021 4:58 pm
I have 2K primer on bare metal that was done right after media blasting a couple of years ago. I have done the metal work and filler work on the car with some sanding that has cut through to the bare metal. I have just sanded the base 2K primer to get ready for another epoxy coat for a solid base.

My question is, I have a 1K epoxy primer that is compatible with the other finishes I will be using. What would be the difference (other than no hardener) vs a 2K as this second coat of epoxy.
I probably have asked this question before, :whoops: but I still can't get my head wrapped around this step and what to use, if it really matters at all. :wink:

I then plan on going with a 2K primer surfacer, then a SS solid color paint.



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PostPosted: Sat Mar 20, 2021 5:45 pm
Assuming that the protection from the 1K and the 2K paints is the same, then the issue really is just the way that each hardens/cures. For the 1K that is going to be by evaporation which means that solvents will be gassing off for at least a couple of days after application. This could create adhesion or gloss problems if you were to topcoat too early. It also means that you'd probably have to sand the epoxy.

For little rubthroughs the 1k is probably perfect, for bigger jobs I think I'd probably go for the 2K.
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PostPosted: Sun Mar 21, 2021 4:53 pm
Hi NFT5,

Thank you for the comment. I do have an additional question, when you say same protection, are you talking that they are a DTM paint or the fact that it is a epoxy and has chemical characteristics that are the same.
The first 2K was not done by me, so I do not know the manufacture as the blasting company has since closed, so all I know is it was a 2K epoxy as requested which I have no doubt about what they said or installed.

I appreciate the recommendation of use vs the size of the rub through (bare metal) this helps me determine where I go next. 1K should be OK as there are no big areas (6-10" sq max) of bare metal.

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PostPosted: Sun Mar 21, 2021 6:00 pm
In terms of protection, I mean both DTM and similar performance and chemical characteristics.

I can go down to the hardware store and buy a can of "epoxy" paint but it won't be anything like an automotive epoxy. If your 1K is automotive paint compatible then you're maybe on the right track. Only way for sure is to read the Technical Data Sheet.
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PostPosted: Mon Mar 22, 2021 6:41 pm
NTF5,

Thanks for the return comment. Yes it is automotive paint by the same manufacturer that I will be using for the primer surfacer and finish SS top coat.

So, it sounds like I'm OK with using what I have as my second coat 1K epoxy primer, then onto the 2K primer surfacer and then after guide coating and sanding it's onto the finish coat of solid color SS paint.

Again, I really appreciate the help provided by this forum and the contributors helping those of us Home Shop Hobbyists.

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PostPosted: Tue Mar 23, 2021 8:12 am
Sorry but I have never seen a 1k "epoxy" that I would put on a car. Also, I would have put four coats of good quality automotive epoxy on blasted metal first, then done work over that. But at this point if I were you, I'd only use a good 2k epoxy even for spots. Jmho...

Wait... when you say you have a 1k epoxy primer are you talking about a spray bomb?



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PostPosted: Tue Mar 23, 2021 9:35 am
Hi Slofut,

No spray bomb, it is a auto paint. I will be using Martin Senour paint sold by my local NAPA parts store. This is the data sheet for the primer.

https://www.martinsenour-autopaint.com/ ... AUTO/PDS/2

Something that I read that maybe some one could answer was, It said you can add hardener to a 1K product as a extra step for a bit better finish. I'm sure it would have to be compatible hardener to the paint. Would this be any benefit or am I making a Mountain out of a mole hill. :knockout: and just need to move on and get it done!!

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PostPosted: Tue Mar 23, 2021 10:47 am
that primer appears to be a single part enamel primer. i know it says epoxy BUT i have never seen a real epoxy that wasn't 2 part, it really isn't suited for any modern day top coats, base clear and possibly urethanes. if you use a single part enamel you can catalyze it with an enamel catalyst that would help POSSIBLY. i would just move up to a 2 part primer then your covered for anything you want to topcoat it with. if you catalyze it you might get by useing an enamel, acrylic enamel, or a urathane top coat, maybe. they all should be activated. your playing with some weird products that could cause problems best to stick with something proven.
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PostPosted: Tue Mar 23, 2021 11:59 am
I agree with badsix, that's an enamel and cheap at that. Very old technology and I'm surprised they're selling the same type product they sold in the 70's. At least get your primers and epoxy from the suppliers here. You'll be way ahead.

And I wouldn't say you're overthinking anything, it's good you asked here before you got really far along.

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PostPosted: Tue Mar 23, 2021 5:18 pm
Epoxy is epoxy, not enamel and not lacquer. There are "epoxy rich" enamels and acrylics but this is not one of those, just a 1K epoxy designed for industrial use.

Is it compatible with automotive top coats? Sure. Is it the best choice? No, I don't think so.

It's quite thin, even out of the tin, with only just over 50% solids, less after 10% reduction, and the volatile components are very fast, leaving it ready for top coating in only 15 minutes which obviates my earlier concern about slow evaporation. The high thinners content has its own problems though with much increased risk of reaction with the edges of your substrate and wrinkling where it gets under it. 2K epoxies don't do this, curing by chemical reaction, not evaporation of a high thinners content. Note that they recommend gun tip sizes from 0.8mm.

Back to what I said before, it's fine for small areas and rubthroughs but I wouldn't use it on larger areas.
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