Epoxy question and filler question

[Craig L]

POSTED A SIMILAR MESSAGE ON HOTRODDERS.COM EARLIER TODAY BUT WANTED TO GET THE SPI EXPERTS THOUGHTS:

Daughter and I took entire 1977 Camaro down to bare metal. We had two quarter patch panels and a rear panel installed. After grinding down the welds on the quarters, we spent 4 hours cleaning the metal on the entire car with SPI Wax and Grease Remover and then applied SPI Epoxy Primer last Saturday. Today, I purchased a gallon of Z-Grip. Before we get started, I had a few questions:

1. Should/can I use the SPI Wax and Grease Remover on the Epoxy Primer before I start applying the filler?

After grinding down the welds, I tried to hammer/dolly the areas the best I could but couldn't get to some of the areas and even the areas I could get to aren't the best. In some areas I will have to fill probably up to 1/8" or maybe more.

1. Should I use a glass stranded filler first (this was suggested to me by the guy at the Sherwin Williams Automotive Supply store) or would the Z-Grip be fine from the start? When answering this question, keep in mind that I may have gotten the metal a little thin in areas due to inexperience in grinding welds.
2. Do either of those fillers have a maximum thickness they should be applied with? In other words, should I do it in "lifts" of x"?
3. On the backside, I sprayed epoxy on the weld seam the best I could but my gun/water catcher/hose is too tall to really get in there very well in the trunk area. I was planning on brushing on some more Epoxy. Would it make sense to also run some grass stranded filler down the weld seam to aid in strength and/or reduce potential water infiltration?

As always, I appreciate everyone's assistance. It was sure a big day getting that thing out of bare metal and one solid color.

Craig

 

[crashtech]

Normally, wax and grease remover is not required in a short time frame if the vehicle has been inside, and not exposed to contaminants like WD40 or Armor All sprayed in the same building. But wiping it down won't hurt.

I do know that I never wait more than a couple days to start the filler work. Once in a while, i notice less than perfect adhesion on filler applications to non-sanded epoxy after 72 hours. If this happens, a good scuff with a red scotchbrite is enough to fix the problem.

Glass reinforced filler is not waterproof. If there are weld porosities or gaps, they need to be sealed from the backside with a thin application of seam sealer, followed by another coat of epoxy. If there are porosities in areas that cannot be reached from the inside, they ought to be fully sealed from the outside by dabbing or brushing small amounts of epoxy into the holes until they are filled.

In my opinion, glass reinforced filler is usually not necessary, though I will still use it in place of lead on quarter panel seams, for example.

Thick applications of filler in one pass will result in larger pinholes, and sometimes panel warping amounts of heat. I'd say about 3/32" to 1/8" at a time is a good rule of thumb maximum.

 

[Barry]

I agree with crash, no wax and grease remover or if you do let set an hour before applying filler.

I have never seen a problem with filler sticking to up to a week old epoxy and testing to 30 days, with no issue but it would not hurt to scuff with 180 by hand if ever in doubt.