Thread: Basic question on epoxy saeler/primer

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I am going to spray some epoxy but have a area of about 1x1 that needs some body filler. Do I need to do the body filler now on the bare metal or can I do it later after the epoxy is sprayed?

I did mine before primer when I did my frame and stuff because I didn't want adhesion problems. But I have heard you can mud on top of primer.

One of our experts like HRP will know for sure though.

Don

I much prefer using filler on bare metal with the metal scuffed to at least 60 grit for max adhesion to it.

If you're using the PPG DP line they talk about this on their data sheet. There are (at least) two schools of thought on this. You've heard the one, the other is based on the tendency (ability) of moisture to migrate through typical polyester fillers. The proponents of filling on top of the epoxy primer believe it to be a barrier to rust forming under the polyester filler. Both methods work, and many shops who are on the hook for warranteeing their work will fill on top of prepared epoxy primers without fear that the "mud will fall off".

"One of our experts like HRP will know for sure though." (QUOTE)

Expert?....Ha! I still learning like everyone else. :-)

I still mud first, but it's because I've done it that way for so long, and it works for me with no problem......however...

The older fillers did not stick to primer and paint worth a damn. Today that has changed, and most of the newer fillers are formulated to stick to sanded paint. Just be sure to read the instructions.

IMO(and others as well)!!! If you are going to use epoxy as your primary bare metal primer then it should be a continuous cover for best moisture protection then the filler applied. When you are finished with the filler prep to your liking, then you re-epoxy to sandwich the filler between epoxy coverings and cover any bare spots from sanding. Next on is the 2K.

BUT, with those good words said, many still do the filler first then epoxy and are sucessful in doing it that way. Which is the right way - I do it as I said first.

Originally Posted by HOTRODPAINT

"One of our experts like HRP will know for sure though." (QUOTE)

Expert?....Ha! I still learning like everyone else. :-)

I still mud first, but it's because I've done it that way for so long, and it works for me with no problem......however...

The older fillers did not stick to primer and paint worth a damn. Today that has changed, and most of the newer fillers are formulated to stick to sanded paint. Just be sure to read the instructions.

Hmmmmm. Could this mean we're gettin' old????????????

I agree with IC2s theory, but all the primer spec sheets mention body filler on bare metal before priming.

Here's a decent general summary -

http://www.roadsters.com/filler/

It states - "In other words, using epoxy primer under filler is a wasted step that may or may not cause adhesion problems later on."

Thanks for the info guys ! I ran out of time and will have to do the filler at a later date. I guess I will just grind or sand the paint to bare metal and use the filler then cover with paint. I am trying to get this thing covered before I leave town and before it rains Sat.

Both ways work. Someone a while back did a study of sorts. Put down the filler on a bare prepped metal sheet, and did another over properly cured and sanded epoxy primer. Put it through several "tests"...bending the sheets, hitting with hammers, etc and the results looked pretty much identical in both test pieces. I have done bike frames in epoxy just to keep the rust from continuing (customers jobs that had set around awhile or were handled extensively). Left them in epoxy till I had the tins ready, then did the filler over the epoxy. Couple of them have been done 5yrs+ with no issues. I think it all just comes down to PROPER prep before any step is done. Good luck! Donny

I use an Evercoat product called Metal to Metal on all the welded seams and any areas that have pitting from rust apparant after the sandblasting. It is waterproof and allegedly won't even allow air to get at the metal. I also use it on welded joints when molding a frame. Used it for years, even back when it was called Alumilead..... I'm sure they had to change the chemistry in the product to keep those meddling feds happy but I still am very satisfied with the results of using the new product.....

How well will the epoxy take a new topcoat in the future? I am thinking it will be easier to spray it with por15 and top coat in a few weeks.

I was ready the directions for the DP epoxy and it says only 2 coats can be applied. This will be kinda hard to do because I am not trying to do a panel, I am trying to do the whole front end. So most of the areas will get hit 2-3-4 times and I dont know the paint will react and bubble or something? I think I will just save the epoxy and just spray the whole thing with por15

POR-15??? As a primer?? NO!, NOT!! NEVER!!!!
Keep that for your rusty wheel wells!!!

Spray your epoxy, I prefer SPI epoxy as it sands r-e-a-l nicely, come back in 2-3-4-6 months, scuff it well with 180 - 320 and lay down your 2K. Sand that with 600 - 800 then paint on your BC/CC.

(Sorry - when someone says POR-15, I just get emotional )

This paint is a year after epoxy, then 2K:

Originally Posted by BigTruckDriver

How well will the epoxy take a new topcoat in the future? I am thinking it will be easier to spray it with por15 and top coat in a few weeks.

I was ready the directions for the DP epoxy and it says only 2 coats can be applied. This will be kinda hard to do because I am not trying to do a panel, I am trying to do the whole front end. So most of the areas will get hit 2-3-4 times and I dont know the paint will react and bubble or something? I think I will just save the epoxy and just spray the whole thing with por15

You may be misinterpreting what is stated. What they're saying is to make your application in 1 or 2 coats. Once cured you can recoat, as stated in the bulletin. Not sure why you're thinking it will take more than two coats at one spray sequence. Since you're going to be away for a while, if you're going to top coat after more than a week you'll only have to scuff the DP. Also note, contrary to what some may believe, under the "Application and Dry Times" section it addresses applying body filler over the DP. Even the roadsters.com discussion addresses scuffing epoxy primers to enhance mechanical adhesion of the body filler. As for it being a wasted step that's likely only a valid comment if you're able to do all the steps from metal prep to top coating within a matter of days. Doing as you've speculated, using DP (or any quality epoxy primer) to seal the bare metal until you can get around to it later, is a plausible reason for epoxying first.