I know that is a leading question with a very tempting answer that won't solve my problem. Here's the deal, is it correct to put body filler over an epoxy primer or should it always go on bare metal under everything else? I've heard that both or OK but there's usually a lot of opinions and everybody has there preference. I'm dealing with pitted metal with some holes that will be welded. Going to use POR-15 on the backside for insurance. I'm leaning toward using a self etch primer over the bare metal followed by epoxy primer, then do what little body filler that is needed, then another coat of epoxy primer then on to a good 2k primer for blocking. Does this make sense or is there a better way?

I always put it on over bare metal in the past, but I've recently been told that you should put it on over a thin, single coat of epoxy filler. The reason is, some body fillers can leech moisture out of the air which can cause the metal underneath to rust, and eventually cause the filler to separate and peel. Sounds reasonable enough I guess.

The way to apply filler for the best corrosion protection is to first apply an acid etch primer such as Spies/Hecker 3688. Then apply Spies/Hecker Vario 8590, which is a two part urethane primer. Sand lightly, then apply body filler. This method gives much better corrosion protection than just epoxy on bare metal.

Gordon VM
Restoration Motorsports

I'm still having a real problem with this idea of bondo over primmer. http://www.chevelles.com/forum/confused.gif I have always been told, seen, and/or read that you needed to get to bare metal to get good adhesion with bondo.

I have a spot that I took to bare metal, used some of Eastwood's metal to metal filler and after sanding I dusted it with acid etch primmer (DPX 171/172) and coated it with a two part urethane primer (K36/K201) (both PPG products).

After it dried, and I was giving it a light sanding, I also changed my lighting position. I found an imperfection (a low spot) that I didn't see before. I am ready to sand back through the primmers to bare metal to fix this spot, but this thread, and others over the last few weeks, have suggested that I could use a light coat of the filler over the primmer. I still can't get used to that idea. Do you rough up the primmer?

On a related topic. I have several deep pits from surface rust on the sail panel on one side that appeared after I stripped the panel. I am going to use a spot sand blaster to clean them out good. Should I use the filler directly into the pits or use the above method of applying an acid primmer and the two part urethane primer first, then the metal to metal then primmer over that?


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70 and 72 Chevelle
ACES # 4051 MCC # 448
TC # 1549 81/70 Cruisers

i have never sprayed hecker before but have been spraying PPG for almost 15 years. randy is right about the bondo over metal, but its not always raining outside or 100% humidity for the moisture to get underneath, but it happens. usually the bondo is primed in the same day. if you apply a few coats of dp epoxy primer they say it holds bondo better than metal. i used the process around my rear glass where some patching was needed and on previous vehicles and had Zero problems. ive also been told that its not good to apply over dp if its been on a vehicle for a long period of time. that i havent tried.


http://budruski.myplace.com/


my suggestion to professor:
when you find some imperfections in the sanded primer it is ok to use some 2 part polyester putty as long as it is minor. scratch it up with 100 grit first. the putty will adhear to the primer and will sand easy with 180 grit. usally what you find is the primer is levelling out the filler to the metal. i usually prime and block and reprime a few times, each time spraying a guide coat to find the low and high spots. for your other question about the sandblasted spots, i would etch prime then dp epoxy then repair. some people blast then apply duraglass and repair. as long as the rust pits are cleaned out good and not have pin holes through you should be good. just check the inside for surface rust too.

[This message has been edited by budruski (edited 03-15-2002).]

[This message has been edited by budruski (edited 03-15-2002).]