Filler over Epoxy Primer

[rick71ghia]

I read the article on this site by Serge on Body Filler Adhesion (very informative - thanks) and have a few questions. I'm using Glasurit 801-1552 epoxy primer. The TDS for the primer does not mention anything about a recoat window. Assuming that I prime the car and then come back anywhere from a few days to a few weeks later and apply Evercoat Rage Xtreme filler, how should I prep the primer? Just apply filler to primer? Sand the primer with P80 or some other grit before applying filler? If I sand the area to be filled to bare metal, any problem if I feather the filler into the primer around the repair area? How would the primer be prepped in this case?

[Serge]

I will tell you what I do...others might have different opinions...

I prefer to use filler on metal, bare metal that is...then epoxy on top of everything...so I would sand the areas that need filler to bare metal using 80 then do the metal. I would not feather onto the epoxy, I would for the sakes of having an even substrate under the filler, feather into metal....

[bodymanhelper]

I agree with serge and thats how we do it at the shop. Bodyfiller always gose over clean bare metal. I put 2 coats depending on what im working on then i cut the skin with 40 on a D. A. and block the rest with 80.

[fireboat]

Serge and Bodyman, I know you guys know of course that you are going against the tide as many tech sheets say epoxy first, then filler, then epoxy again.

That said, I always found that method odd because in fiberglass boat repair, the cardinal rule is epoxy over epoxy or polyester (auto filler is polyester resin) but NEVER polyester over epoxy because of adhesion problems.

Yet, with most autobody repair, it is done the opposite,...polyester over epoxy. Heck, I do it this way because I am just an amateur home painter and this is what most everyone says to do. But, I still find it troubling because of my experience with fiberglass boats.

I guess the bottom line is that both ways work and there are pros and cons either way.

[Serge]

Show me one tech sheet from a filler mfgr that says to put their product over epoxy...Not epoxy mfgrs who want to sell more epoxy...but filler mfgrs that don't want their products to fail...

They all say the same thing...over bare metal...Did you see my test on this site? I was expecting better performance from the epoxy to filler bond...The metal to filler bond was flawless though...

I would be interested in seeing the tech sheet you are talking about. Can you post a link?

[Len]

I had an argument with a paint salesman on the Hotrodders site about this. The question I asked that pretty much ended the discussion was.... OK if I apply filler over epoxy then sand the filler do I need to apply MORE epoxy over the bare metal before I apply more filler?

This application of epoxy before filler is a selling aid by paint companies to sell more primer. Like Serge said, you won't find a filler company telling you to use primer under their filler because they would sell less filler, it's all paint company talk.

With all that said, we prime metal that we strip if it's going to be undergoing repairs for a longer period of time. If it's a quick repair we don't prime. If the surface damage is very minor we may scuff the primer with 80 then fill over it but with a surface that needs any significant amount of filler we remove the primer, do the filler work then re-prime over the filler.