I did somebody work on the outside of my car. I grinded out and welded a sheet of steel onto the body to fix a rust area. I then put a little Bondo on top to smooth it out and some primer to seal it up temporarily. Anyways, I went to the local paint shop and the guy told me I should have put some "sealant" on top of my welds before the Bondo. This would help prevent it from rusting on the weld. Is this nonsense or something I should do in the future?

a little etch primer under the plastic would not hurt. the way you did is fine , i;ve worked in a few shops and they all did ther plastic work the same way . you could put rust preventive behind your patch.good luck and hope this helps.:thumbsup:

If your welds are free of pinholes you'll be fine. If not, moisture will get behind the bondo and it will bubble, ruining your paint job.

Tom

If your welds are free of pinholes you'll be fine. If not, moisture will get behind the bondo and it will bubble, ruining your paint job.

Tom

How long do you think that would take.

shoot some epoxy primer down before doing the filler work. Then use seam sealer from behind.

If your welds are free of pinholes you'll be fine. If not, moisture will get behind the bondo and it will bubble, ruining your paint job.

Tom
Chances are pretty slim of getting no pinholes unless you're an exceptional welder. Trouble is, you may have some so small they're not noticeable. I always coat my welds with waterproof resin jelly then grind that down before applying plastic filler or epoxy primer.

How long do you think that would take.

:( Sadly. not long at all. Days, maybe hours to start the process depending on how much moisture gets in there. Why?

... and some primer to seal it up temporarily.

Regular primer? Regular primer is porous, and will NOT "seal" it up...

Weld
grind
epoxy prime
fiberglass resin jelly filler or metal 2 metal filler
plastic filler
block
high build primer
block some more
guide coat
block some more
seal
paint

I use a skim coat of a product called "All Metal" by USC over my weld seam's. Its like "metal 2 metal" and is moisture proof. You can then do you normal filler , prime , paint over that.

All those extra bondo products sounds like too much work to me. Ive never used fiberglass based fillers or that all metal stuff over welds, dont see the point.
I guess if one has pinholes in the weld then 'glass is a good idea, but a weld seem without pinholes complete waste of time.

Etch primer and filler dont mix!!! Am not aware of one single etch primer that says you can apply filler over it. You can apply etch over the filler but not filler over etch.

Agreed Eric, nothing will stop the bubbles if you have pinholes in your welds, or small pinholes of rust you may have missed. I just did the porters S-10 cab corner, didn't want me to cut it out and replace with metal. Blasted it and used Duraglass, undercoated the heck outta it with honey coat and thick black undercoat, starting to bubble 2 months later where there were no bubbles before. Once it starts rusting from the inside it could be 4-5 inches past where you actually see the bubbles. If it's a lighter color and down low you'de be better off glueing a patch in than welding, if your not the best welder in my opinion.

I use epoxy primer over bayer metal regardless of what the next step is.

fiberglass reinforced filler (like Duraglas) is waterproof, is it not? Just put some of that down first.

fiberglass reinforced filler (like Duraglas) is waterproof, is it not? Just put some of that down first.

Andy, I believe the more proper term is water resistant. IMO the ONLY water proof solution is a good solid weld.

I found this, and I don't know this guy or anything about what he knows, but it is interesting what he says, check it out.

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

Rob

I found this, and I don't know this guy or anything about what he knows, but it is interesting what he says, check it out.

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

Rob


Thats a good read, Rob. I picked up a couple of things in that. Thanks.

Your welcome Steve.

Rob

Weld
grind
epoxy prime
fiberglass resin jelly filler or metal 2 metal filler
plastic filler
block
high build primer
block some more
guide coat
block some more
seal
paint

You make it sound so easy...:noway:

Etch primer and filler dont mix!!! Am not aware of one single etch primer that says you can apply filler over it. You can apply etch over the filler but not filler over etch.

I'm afraid I have to disagree. RM EP 589 for one. I use it as an etching primer/ vapor barrier all the time before filler. Haven't had a problem yet.

Notice I said yet...:)