Painters I have a problem......

[kevin2502000]

This is actually a problem concerning my car . I repainted it last year and it was rusted by the fuel fill door. I used naval jelly, cut out the rusted part, ground out everything welded in new metal. It still bubbles the paint. I think its because the rust isn't "dead" and is creating the bubbles. It's really annoying and I want to get it right this time. There is body filler over it and was primed. Any old timer ideas?

[rexazz2]

if it was left in just primer that is your problem
primer is poreous
primer will allow moisture to penetrate

[kevin2502000]

No it was painted over the primer. The paint is whats bubbling. I mean that after I repaired the metal I primed and painted it.

[chinto]

just means you didn't get all the rust.

[kevin2502000]

I got everything I could see soaked everything in naval jelly. Any tips to kill it?

[Erki]

Is there a seam in the panel by the fuel door. maybe you have moisture getting between the metal or behind the metal. May have to seam seal it to seal it right off.

[Astro4x4]

Correct me if I'm wrong, but Naval Jelly is acidic right? So did you neutralize it prior to filling / priming? I like Rust Bullet myself and have been using it for 4 or so years, so I can say it works. With all the salt we pour on the roads here in the winter, I need all the help I can get.

[kevin2502000]

I didn't neutralize it but I cleaned it off good with denatured alcohol. It is a double walled panel, I filled it back up with expandable foam since the other stuff burnt when I welded it. Keep the ideas coming!

[Erki]

Also did you etch prime the bare metal before you primed it?

[kevin2502000]

no I did not, what exactly is that? This was my first painting experience and I used Acrylic Enamel (Nasson) but I learned alot and when I repaint the errors I was thinking about BC/CC. Any suggestions either way?

[Erki]

etch primer is an adhesion promoter that should be sprayed on bare metal. My boss says rust will come through if its not used. I wouldn't know for sure because I always use it if there is any bare metal showing before primer or paint. I believe you can even pick it up in a spray can just for small spots. Ive never used it but have seen it.

[starion88esir]

I didn't neutralize it but I cleaned it off good with denatured alcohol. It is a double walled panel, I filled it back up with expandable foam since the other stuff burnt when I welded it. Keep the ideas coming!

There's one problem. Expandable foam traps moisture inside of panels. I've seen it on numerous cars that have come through our shop. It's not good at all for the panel. Also, you need to make sure you neutralize all of the rust before repairing it and painting it, or as you've witnessed it will come back. Rust bullet is a good neutralizer, por-15 has some good products. Naval jelly is not sufficiant. I guarantee you there was still rust on the inside of the panel that had not eaten all the way through and it just spread, aided in part by the expandable foam.

[kevin2502000]

Ok thanx I will dig out the foam as best as I can and use rust bullet? Where can I get that at and what are the thoughts on the paint? Acrylic enamel easier to work with than BC/CC?

[Erki]

Ive only sprayed base/clear.

[chinto]

base coat clear coat is the way to go, but be prepared to cut and polish as well. This means more money on supplies and equipment, but the results are 100 times better. Nason bc/cc is pretty forgiving and sprays well.