Spi epoxy, then poly. What’s your opinion?

W

Wackerjr

Restoring a 65 Chevy C-10. Entire vehicle dustless blasted ( hold-tite wash down, was done 3 years ago) . Have been working the body for the time after that, getting real close to done. Almost ready for primer. Body has been currently bodyworked over bare steel, and sitting at 80 grit.

I used Spi on a Camaro years ago. Same process, epoxy over filler, then spi 2k, epoxy, then spi finish. (Spoke with Barry at length on that one) .. love the products.

I have already purchased epoxy, been using in all the inner panels, and where panel replacement has occurred.

Really wanting to poly this vehicle. I have however never used poly. Looking at slick sand or G2 I think...

Long post sorry... more info the better....

Question is I can “rent” a bake booth for the weekend. Tired of painting in the garage.

Is baking epoxy recommended, should I just poly over filler and steel?
I’m thinking to epoxy first, then poly, then epoxy seal and finish. Obviously with lots of poly blocking in between. Can I even do epoxy, and poly in 2-3 days?? Should I bake?
Thoughts? Is there a better process?


Thanks in advance. Long time reader, first time poster..
 

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Epoxy is always the "correct" choice. :) Spraying Epoxy, make sure temps are 65-70 both in the air, on the metal and the epoxy as well. This is very important as SPI epoxy needs to be at least 65 degrees (70 would be better) for at least 24 hours straight. Setting it out a full day in the sun helps a lot too. I would consider that almost mandatory especially if I was applying poly primer over the epoxy. Give it a minimum of 48 hours before applying the poly primer over the epoxy. This is very important.
As for your question about baking it, I wouldn't do it. If you did you would want to keep it at 120 degrees, no warmer than that. But epoxy cures differently than urethanes. Epoxies need time more than intense heat. Even if you baked it you would still need to observe the above times. Otherwise you risk the epoxy not curing correctly and having to re-do everything. Just keep in mind 24 hours @65-70 degrees. Put it in the sun for a full day if possible. 48 hours minimum before applying Polyester primer.

Just a note about poly primer. It fills good, sometimes too good. :) Don't pound it on because it builds a lot. Two coats, block, then re-apply if neccesary. That'll help from building up too much around edges, opening etc. You'll want to use a fairly coarse paper for your first round of blocking with it because of how it builds.
 
For those that have used poly, what do you spray after it before base? Epoxy sealer coat, 2k high build, else?
 
Duh, i missed the picture.
To answer your question not for the stress cracks now.
 
Recommended polyester? Lookin at evercoat slicksand, or Featherfill G2. Any better than others?
 
Personally, I use the G2 but that is all I have ever tried so can't say anything about Slicksand.

You will need some Acetone on hand for thinning and easy clean up.

If you haven't used a polyester primer before pay very close attention to set up time. This is like spray on body filler in that it is a chemical reaction that makes it cure. There is no flash time or grace period with this stuff and if you have some in your spray gun when it kicks your gun will be seriously plugged up.
 
So it's not recommended to put epoxy as a primer over blocked slicksand? Or is that ok? I already have more film build on my car than I want.
 
So it's not recommended to put epoxy as a primer over blocked slicksand? Or is that ok? I already have more film build on my car than I want.

There is no problem with epoxy over sanded poly. Once you get everything blocked down, a coat or two of epoxy would be perfect to fill scratches 180 or finer and to seal off your body work.
 
Thanks Strum, thats the plan and I'm almost there. I'm thinking I'll put two or three coats of epoxy to seal off the finished bodywork it'll prob sit that way for a couple or a few weeks, then when it's time to base I'll block sand the epoxy with 400 and put a coat of reduced epoxy as a sealer before base. Sound ok?
 
Especially if you are thinking of spraying 3 more coats of epoxy, you should consider starting with some coarser paper. 220 dry until 90% of the gloss is off of the epoxy then 320 for the last 10% is my preferred method. You could DA or wet sand to refine the scratches from there if need be.
 
So it's not recommended to put epoxy as a primer over blocked slicksand? Or is that ok? I already have more film build on my car than I want.
Not trying to be a smart*ss, but if that is true, maybe the poly needs to be blocked down more. Also it should be sanded off of edges and cut out of holes, serious chipping problems can arise from leaving too much material. I've seen guys get heartbroken by accidentally breaking large chips out from around holes during re-assembly because they didn't think ahead enough to keep the primer out of there.

Same thing with panel edges, if you accidentally bop them together during reassembly, if there is a lot of 2K or poly on the edge, it's going to break off a big chip. But if its a couple coats of epoxy and a paint job, little mishaps will usually have no effect.

Not meaning you particularly, but I see this commonly with hobbyists, where the solution to a problem is always more primer. That can be true to a certain extent, but there is NO substitute for making sure excess build is removed as much as possible, and that takes a LOT of time if it's being done right.
 
Thanks Crash. The film build is in the previous paint jobs, not necessarily the poly. I did block the poly down to level with the previous paint and I've cut down all the edges, holes etc... crazy how much time these things can take. But the car is getting very long in the tooth and I couldn't afford the time to strip it, although I DA'd and blocked (220 wet) most of two paint jobs off the damn thing before starting the bodywork. But there is no more poly on there than it takes to make it flat. Did I mention its a c3 corvette? :rolleyes:

And I apologize to the OP for hijacking this thread. :(
 
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