Epoxy Primer after 7 days

Gilles

New Member
I've been using SPI epoxy primer for several years now with great results. Been working on a restoration project for many years and recently stumble on a post in this forum that stated I should DA sand with 180 and re-spray before applying any kind of filler and 2K primer if its benn more than 7 days. I've only been scuffing it with maroon scotchbrite and then putting on filler and 2K primer after that, months after applying epoxy primer. So far no problem with adhesion. That said, I am somewhat concerned that I may have problems down the road. Should I be going back to bare metal or will it be ok the way it is ?

Gilles...
 

Barry

Paint Fanatic
Staff member
I d say your ok if none of this were done after the epoxy was a month old.
Use 180, and the instructions are there to protect you.
 

Chris_Hamilton

Trying to be the best me, I can be
Sounds like some of it was done at least a month after application. Hard to tell how good adhesion is just sitting there as well. You could try a scratch test of sorts. First simple, simple test is go to an edge where the filler is feathered into the epoxy. Using your fingernail try and scratch the filler away from the epoxy. If it lifts off, that is not good. Also try using a razor blade and do the same thing. Use the blade to scratch it (shave it) away from the epoxy. Success would be it being very difficult to remove, or scratching results in both it and the epoxy being removed from the surface. If it comes off and the epoxy stays consider that failure and would probably be a good idea to re-do those areas if you are concerned about longevity etc.
 

Gilles

New Member
Thanks for replying guys. I will give the scratch test a try. I only work on this weekends so the 7 day rule is a bit hard to conform to in my case.
 

Barry

Paint Fanatic
Staff member
So many factors here but the general rule.
Paint 7 days re-epoxy.
Body filler up to 3 weeks 180 and apply
Same with 2k primer.

Before I say stuff like this, I usually ask many questions, so this is the general answer.
 

Gilles

New Member
Just did the scratch test and the layer of epoxy over top of the filler came off very easy, however; the filler came off with the epoxy when I scratched all the way to bare metal. So I think I need to go back a least one layer.
 
Better to be safe than sorry.
Reading and following the Tech Sheet is absolutely necessary for all the materials you use.
I found out the hard way that using Metal Prep/Phosphoric Acid without neutralizing ruins your paint job. Didn't show up until I was buffing the clear coat and a blister kept rising up and then going back down whenever the buffer went over that area. Ended up cutting the blister open and the paint chipped off all they way to the Metal Prep. Had to strip the entire panel back to bare metal and start over.
 

crashtech

Combo Man
When time is limited, there are things that can be done. Get an inexpensive heat lamp, and do one panel at a time. Strip and prime one day, apply filler the next.

 

Slofut

Promoted Users
Maybe if you know a part or project could be months in epoxy, how about epoxy on bare metal, wait 24hrs and apply a couple coats 2k? That way the bare substrate is sealed in epoxy and the 2k can be used as a base for filler and bodywork later? Is that acceptable?
 

Slofut

Promoted Users
Ok crash and tex, thats what i needed to know. Ill always put spi epoxy on everything first. I’ll deal with the time windows. ...and temps
 

Gilles

New Member
Thanks for all the info, I think I will follow Crashtech's suggestion and get a heat lamp. My Garage is heated at 18 C (64 F). The heat lamp should help with the filler as well.
 

giggity

Promoted Users
So technique question....

I epoxied after I blasted full car, then went back to repair, sanded epoxy on repair areas, some all the way to metal. I put all metal filler direct to metal on several spots.

I scuffed or sanded rest of car again. I plan to epoxy again, hopefully 2 full coats. I should wait at least a day to apply rage gold filler.

Should I apply filler to whole car, like a skim coat? or just areas I know will need it?

I plan to spray 2k after filler.

How long do I have after the filler, sanding included to apply 2k? Would I need to scuff everything before applying 2k?

Currently Im waiting for a dry warmer day to spray. Im in Houston, we have a lot of humidity, and its been around 60 degrees lately. I usually warm up garage to 70 with a propane heater before doing anything.

20210118_202132.jpg
 

Slofut

Promoted Users
Do you have large dents or something to fill with Rage? I don't see anything in that pic. As it looks to me, I would put three or four coats of epoxy on and bloc sand with long blocks and 180 or 150. Then guide coat with finer grits to 400 or so.
 

giggity

Promoted Users
Do you have large dents or something to fill with Rage? I don't see anything in that pic. As it looks to me, I would put three or four coats of epoxy on and bloc sand with long blocks and 180 or 150. Then guide coat with finer grits to 400 or so.
yea the rear quarter has some repaired spots, I cut out the lower area that always rusts on these cars, and welded in patch. It shouldnt take much, but will still be needed. I had more All Metal down, but ended up sanding most of it off.

a few small areas on doors. and where the rear quarter meets roof, there is a slight concave area on the weld. I had a few areas I had to sand down, which will probably require no more than 1/8 inch...not sure I can make that up with paint?


20200729_203800.jpg




20200525_131032.jpg
 

Slofut

Promoted Users
I would epoxy that at least three coats and use filler on top and block sand with 150 to see where you're at. I can't imagine spreading the whole car with filler, that's stuff you see those guys do on television, no need for it unless you have hail damage all over the whole car :D
 

crashtech

Combo Man
It's important not to use 2K urethane until it is known for sure that more filler is not required. This is a mistake that gets made often by less experienced technicians. Applying a few coats of epoxy all over and blocking it is a good way to see if the body is ready for "prime time," so to speak. 2K primer cannot magically fill imperfections that are easy to see and feel. It's put there to give a final uninterrupted (no sand-thrus) perfectly straight surface for paint. Typically an older vehicle with repairs is going to need many areas glazed with putty and either several rounds of epoxy and blocking, or a round of polyester primer before being ready for final 2K.
 

Chris_Hamilton

Trying to be the best me, I can be
I like to epoxy, then after the required cure time, apply filler or glaze everywhere it's needed. SPI epoxy has a sheen to it which will help you see any areas that need filler. Then sand the filler at your leisure. When doing this I like having 3 coats of epoxy as my base which makes it a little less difficult to sand through to metal. That way if you have to reapply filler you can do it over the sanded epoxy/filler.

One way to save some time , if you have an area that you think will take multiple applications of filler to get correct, use a "cheesegrater" and work your first application down with that. Once you have worked it down close, lightly sand the cheesegrater marks (if you don't you get pinholes) and apply more filler. Saves you from having to apply filler, sand through to metal, then apply more epoxy, before applying more filler.

Applying filler over epoxy means that you sort of have to re-think how you apply your filler and how you sand it, especially if you are trying to not have to re-apply epoxy, then more filler.

When you have the filler work done, always re-apply at least two coats of epoxy for best results.
 
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