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Scuff epoxy before filler?

#1
I am inside the recoat window (it’s been 48 hours). I want to apply Everglass filler over the epoxy. The epoxy coat is so smooth I’m afraid if I don’t scuff it that there won’t be very good adhesion. Will it hurt anything to hit it with a 3M paint prep scuff pad?
 
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Chris_Hamilton

Trying to be the best me, I can be
#2
Recoat window is up to 7 days. No need to do anything. ZERO need to scuff it. Just go ahead and put your filler on there. Bond between the filler and epoxy is adhesive not mechanical (scratches) and is far more powerful than a simple mechanical bond. You will be fine. No need to rethink it.
 

Chris_Hamilton

Trying to be the best me, I can be
#4
Why not just sand it with 220?
Because you are somewhat defeating the purpose of using epoxy! It doesn't need to be sanded before you apply filler. It is designed to be used that way. Directly over unsanded epoxy that is within the 7 day window. It actually will lessen the bond between them if you apply it over sanded epoxy. Maybe Barry will chime in.
 
#7
I did not sand the epoxy. I put the Everglass right on it. When I sanded, I sanded off some of the neighboring epoxy. Now I have to reshoot the bare spots before continuing on with the filler work. Such is life I suppose.
 
#10
I did not sand the epoxy. I put the Everglass right on it. When I sanded, I sanded off some of the neighboring epoxy. Now I have to reshoot the bare spots before continuing on with the filler work. Such is life I suppose.
That's typical. Myself, I primed, filled, sanded, primed everything again, filled, sanded, and repeated the process until the surfaces were perfect. Sandwiching the filler between layers of epoxy primer pretty much gaurantees that I will not have adhesion problems. I never applied filler to bare metal, only to epoxy or itself.

Takes a little longer but the end result is unbelievable.
IMG_20190926_123127143_HDR.jpg
 
#11
If laying epoxy down for the initial foundation I shoot two coats mixed with no reducer. After 24 hours I will lightly block sand with 150 grit just to reveal the low spots. It works like a guide coat with the low spots remaining shiny. Apply filler to the areas that need it feathering into the surrounding epoxy.
No need to sand the low spots prior to filler if within the 7 day recoat window.
 
#12
Sounds good guys. I will be recoating tomorrow.

Nice pickup @64avanti. We have a 1953 F100. Was my great grandfather’s farm truck. Dad got it when he died. We restored it (mostly), got it running, and took it to see my grandfather. He got to ride in it before he died. We got it home, and parked it. Next time we went to start it, we found the motor had seized. It lived just long enough to get my grandpa his ride. It’s a flathead V8 and I think the block or head cracked and allowed coolant to seize the piston. I plan to pull the engine and find the issue after the Dart is done.
 

Chris_Hamilton

Trying to be the best me, I can be
#15
Past 7 days you want to sand the epoxy with 180 grit, by hand or machine before applying more epoxy. Good idea to do that even if you still have filler work to do. Apply the filler over the fresh (24-48 hours) epoxy rather than applying the filler over the sanded epoxy.
 
#16
so filler sticks better to smooth fresh epoxy, than sanded old epoxy? interesting.

I dont doubt it, I painted something in my garage, my flooring in garage is epoxy(not SPI), got a drop of SPI on floor, tried to scrape the SPI of floor, it took with it the garage epoxy...
 
#17
so filler sticks better to smooth fresh epoxy, than sanded old epoxy? interesting.

I dont doubt it, I painted something in my garage, my flooring in garage is epoxy(not SPI), got a drop of SPI on floor, tried to scrape the SPI of floor, it took with it the garage epoxy...
Yeah this is some great stuff. There is a video out called the SPI torture test or something like that. It pretty much shuts down the naysayers.
 

elwood

Registered Users
#18
I've never had a problem with filler over properly cleaned older epoxy. Done it plenty of times. Just make sure it's sanded and cleaned properly. Now if it's older than 6-8 months old I respray with fresh epoxy then do filler next day.
 
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