how to stop rust even after you grind it out

[c00nhunterjoe]

going to tackle some body work tomarrow, pure backyard work, not professional by any means. i am goign to strip, grind, prime and paint. but i keep having the rust come back through the current primer on the car. i know primer isnt a selaer but the car is parked out of the weather and the rust keeps coming through the primer. i sanded to bare metal, then went to town with a wire wheel before priming and i still get the rust specs showing up through the primer after a while.  i hate to go to all this work tomarrow to have the rust come through paint as well....... opinions?

[tricky lugnuts]

Not an expert by any means, but what kind of primer are you using?

They're not all created equally. I sprayed my Charger in epoxy primer (I think that's what it was - DP something?) and it kept the rust down for like 2-3 years before I painted it. Some primers actually soak up water, allowing the metal underneath to rust if I'm not mistaken. You want the stuff that doesn't do that. It costs more.

That or maybe you just need to take down the metal farther first, maybe ditch the wire wheel for some sandpaper to get every last little speck of rust off before you prime. Also, after you prime, maybe you want to spray on some sealer.

[c00nhunterjoe]

i used etching primer to make it a bit forgiving in my abilities.....

[riggs626]

 I treat the metal with an acid etch basically chemically treat it

[superbirdtom]

goop some extend on it and let dry and then prime and paint over it. NAPA has extend rust stopper

[71green go]

If your using a lacquer based single stage etching primer with reducer or an acrylic single stage primer then yes it will not keep moisture out like a two part epoxy primer with reducer........spray bomb etching primers are also not very good..
Invest in some two part primer epoxy and a respirator, even the cheaper Omni lines of paint will make a world of difference.....usually a gallon kit for under a hundred bucks.
Don't skimp on the prep!