Epoxy hold out better than Epoxy with/filler on deeply pitted metal?

B

Brad J.

Oldtimer
I'm working on a car with heavy pitting in the sheet metal. I've blasted the surface to clean/pitted metal. Normally I'd do two coats epoxy and then wipe the panel with filler and work from there.

I've been thinking about using only the epoxy to fill the pits. I'm not on a time frame so it can sit. I've been an epoxy only guy for the past five years other than fillers. Does anyone know if holdout is better with epoxy only over the epoxy/bondo I would have done in the past?

I want the best holdout available and I've had great results with filler but maybe the only epoxy bit is better?
 
I'm using it for that very reasoning. I'm in the final blocking of some fenders and keep finding small low spots that I over fill as best I can with an artists brush (but thinking maybe an eye dropper) and come back to sand it when I'm ready and move on to other things.

Have you let a 1/4" or more cure in a jar and pulled it out after a month or so yet?
 
The holdout on the epoxy is great and u can use it for surfacing as well however it isnt as practical/efficient as the other products available on the market which is what most shops are looking for..
In your situation with time on your side, experiement with the epoxy and see if you like how it performs as a surfacer..

Personally I think if you have to work the metal anyways why waste the time and precious epoxy ( Yes I love my SPI epoxy ) when you can poly over it or wipe it or whatever combo you need to make the panels straight.. If you waited and used epoxy to fill the pits, then either poly or skim coat the panel, I think you are defeating the purpose..

Now if your panels are pretty much straight and you just want to use as a surfacer, great idea and you can use as many coats as you want as long as you allow enough flash between each coat.. Baking in sun helps allot too speeding it up especially if you are building coats with it.
 
We do a little of both on pitted panels, several rounds of epoxy and blocking before switching to poly putty on ones that are just too deep. I'm happy with how this works out. It's usually too much to ask of the epoxy to fill the deepest pits, unless you want to drop it in there off the end of a brush.

Holdout is excellent either way, I can't tell the difference.
 
I have the trunk lid picked/filled/shrink disked and three wet coats of epoxy. I think I will let it sit a couple weeks, 80 block it and hose three more and see where it's at.

In the past I would have skimmed the epoxy with poly and have had outstanding results but not 10+ years of concrete proof of holdout. Wife's Auburn was done in the early 90's and every year more pit areas are coming through. It was DP40 epoxy with Laquer topcoat. That epoxy has held up a long time and her grandfather never used poly of any sort so I know there isn't any poly in it.

Thanks for the info.
 
Given the lacquer topcoat, any chance grandpa might have glazed it with Nitrostan, or maybe filled some of the remaining imperfections with lacquer primer? I don't remember being able to use DP40 as a surfacer, it didn't sand well at all. But that was a long time ago, I could be wrong. Certainly compared to the K200 I was using at the time DP40 would not have seemed like a friendly surfacer.

I think SPI epoxy is as bulletproof as it gets, but I don't have any problem sandwiching a bit of poly putty in between layers of epoxy. I'm running under the theory that the epoxy penetrates the filler a bit and seals it against oxidation and the elements, protecting it much the way it protects metal.
 
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