Sit in 2k or Epoxy

T

Tiggie

Beginning hobbist here.

If you needed to let a car sit a couple months, would you leave it in 2k primer or epoxy? Why?

Car is garaged indoors, and nothing is happening in the garage (not even cars in/out). I plan to cover it with plastic as well just to keep any dust away.
 
Generally I'd say epoxy just because it seems to be a better protection from any contaminants... But by what you describe, I would lean towards 2k primer simply because you would not have to sand and recoat like you would if epoxy..you could just clean and start body work or blocking. The high build would need to come off if any filler work tho. Extensive filler work would probably change my plan and leave in epoxy. My 2 cent
 
Don't cover it. It will build up moisture under the plastic.

The pros will tell you to use epoxy all the way through. Use the epoxy first, especially, on bare metal. It will seal it up and help prevent moisture intrusion. When ready for filler just scuff it and do the work.
 
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First, why are you priming it? Is it in bare metal?

Epoxy is always the proper choice for superior corrosion protection and adhesion to bare metal. If I had to store something for a period of time, absolutely epoxy. Urethane primer is only for surfacing. That is its proper use. It's not designed to go over bare metal nor will it provide long lasting corrosion protection as it is porous. People do it but that doesn't mean it's correct.
 
My understanding of the question is what to LEAVE it in..I would never trust epoxy outside its recoat window to just scuff. I would scuff and reapply. I don't paint full time but have left many a job in epoxy/2k for months as I worked the car with no ill effects.
 
It would depend on what stage the body was at. If it needs more work, leave it in epoxy. If it's about ready for paint, leave it in urethane primer, if that is going to be used. If you aren't sure, leave it in epoxy. Don't cover it, but also don't use any aerosol oil products like WD-40 or penetrant oils, or anything like Armor-All or tire shine anywhere near it, like not in the same building at all.
 
Thanks for the feedback. I should have been more specific.
The main shell of the car is in 2 coats of epoxy, body work done, with epoxy on top and below that. If I had the time, it'd be going 2k and blocked out, then base/clear time. But life gets in the way.
I am on day three of my seven day window.
From what I am understanding, I can go ahead with 2k since I'll need to block it out anyway. That will save me from scuffing the epoxy, and it should be fine in the garage. Sound okay?
 
Not everyone will agree, but it is fine from my point of view, just take care not to introduce contaminants, this is especially important with 2K as it is more porous than epoxy and will soak up whatever lands on it.
 
Keep in mind that 2K can get like concrete to sand if you let it cure for more than
several days. Whatever you leave it in, it will probably be so hard to sand that you will
want to use coarse paper, which means you'll probably want to re-prime anyway.
It would be easier to re-prime than trying to sand all the scratches out of old 2K.
 
So several month old 2k sands harder than equivalent age epoxy?

My thoughts behind the 2k was basically sand it several months into the future, and spray my base on that. Thinking now that may cause some adhesion problems between the base and the 2k. Am I on the right track?

So I'm thinking now to leave it in the epoxy, which is 2-3 coats deep depending on location. When time allows to continue my project, scuff the epoxy, apply a reduced epoxy as a sealer, then 2k and base. Again, am I on the right track?

What kind of skrinkage does 2k have?

What kind of scuff on the old epoxy when the time comes? Are we talking red scuff pad or nice gritty paper?

I'd be pretty lost without this forum, plus getting robbed by the local paint store.
 
I don't have a problem sanding cured-out urethane. It is harder to sand, but nothing like polyester primer, for instance, which is the true concrete of primers. It does take longer to sand fully cured primer, but at that point you know that it is very stable and done shrinking. For custom work, and for hobbyists, I think that waiting longer is always better, even if it does entail more elbow grease.

You might be overthinking this a bit. It's really personal preference in a way, once you have more experience working with both products, you'll know for yourself which way you want to leave it.

I have not experienced adhesion problems between cured 2K and base, the key being to activate the base and use a slow enough reducer to get some bite into the substrate.

Of course, the SPI recommended procedure (detailed here) is to use reduced epoxy as a sealer, so if procedure is to be followed, there is no concern about the type, age or adhesion properties of the substrate.
 
I scuffed my epoxy tonight for peace of mind and also to sand out a couple spots of orange peel. Cleaned with Waterborne WGR to sit overnight.

Plan is to tack and spray the 2k tomorrow.

The epoxy left alone scares me a bit by letting it fully cure without top coat and I have read (maybe a bit too much) about how nothing besides itself likes to stick to it after the window expires. I know another coat would fix it but at that point I'm starting to get a lot of paint on the car by the time it's done. I like the stuff though. Sands easily and seems to stick to the metal as advertised.

So it's not crazy to spray base over well cured and well sanded 2k?
 
It's not crazy, but it's also not the SPI recommended procedure. Sealer is best before base.

The reason I choose not to many times is because sealer is difficult to manage in jambs, unless the jambs are being painted simultaneously with the rest of the vehicle. Color and clear won't completely cover the sealer in the jamb, so to do the sealer step correctly with already painted jambs, the vehicle has to be masked twice, once for sealer, with the jamb tape/foam very close to the exterior edge, then again for color and clear with the jamb tape farther in, so the edge of the sealer gets more completely covered with color and clear. Clever masking can make this step easier if the rig is taped so the doors, hood, and deck lid can be opened without destroying the rest of the tape job, but it still adds work.

Just my 2 cents, I know there is some disagreement on this point, so don't take my word as gospel.
 
There will be a lot of opinions but for mine: Leave in epoxy. Sand and spray a reduced (sealer) of more epoxy before you start work again. This reduced coat will not add enough millage to matter. I've gotten contaminates on 2k that have been significant enough to have to sand out and re-prime from cars sitting around. Epoxy seems to lock up tight enough that after a few days, nothing can penetrate or stain it.
 
take a scrape of sheet metal and spray one side with epoxy and one with 2k primer. leave them outside.
 
Shine pioneered the excellent technique of using epoxy-only instead of switching to 2K in the last stages, and I believe some other members have successfully done this as well. Epoxy blocks very well, and during the process of using it as a surfacer for blocking, there is no shame in putting a swipe of filler or putty here and there to correct problems as you go, in fact it's made to do that, unlike 2K urethane. I use epoxy that way up to a point, but still switch to 2K urethane for the very last blocking session, when we're sure that the body doesn't need any more filler. This eliminates needing to use things like polyester primer or heavy coats of 2K urethane to get things straight, but still allows 2 or 3 step blocking of the final primer.
 
2k is on. Break time for me (it's actually work time - work gets in the way of car progress). Will sand/block when the time comes. Probably do a reduced epoxy sealer coat before the base to be safe as well

The tech sheet wasn't kidding when it said clean your gun between coats. This stuff cures quick. I cleaned my paint gun, but left some in a mixing cup longer while doing daddy duty for a few minutes. Stuck to the mixing cup very well!
 
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