Hi. I got another project car, it is real straight and all there, BUT the roof has a rusted area about 12 inches wide! I really feel that the car is not worth cutting the top out and tring that.

So, I sanded out all the rust I could, there was a little left in the metal. So I used rust convertor and let it dry the 24 hours required. It dries to a sandable primer.

When I got it ready to paint, I cleaned it with paint prep and all the black rust convertor came up. I was told that the rust may be treated, and to spray it with etch primer. I had some left, so I sprayed etch over the bare metal and light rust, then with 2k primer.

Do you think the rust will return under the paint soon?

Also, I heard that etch primer makes your paint get tiny bubbles in it after awhile. Is this true or just inproper primer/sealer under the paint?

Thanks
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What exact products were used? Etch primer cannot be related to the tiny bubbles you've been told about, unless the primer that was used was not recomended for a direct topcoat application. An example would be Dupont's variprime which is not designed to be dirctly painted on. Some etch primers need to be sealed prior to topcoating and I have seen adhesion failures that were a result of painting directly over self etch type primers. As far as rust coming back it's a gamble whenever you apply primer over rust. The best bet would have been to remove the rust completely. Muriatic acid works good for removing those tiny little black specs left in the pits after sanding but is definately a health hazard. If your primer and paint can keep oxygen from re-energizing the rust you'll be OK. Rust needs oxygen to grow period. If a rusted object is sealed from oxygen it will lay dormant. A good example of limited corrosion is a closed boiler system, closed meaning no new water can enter the system. In a closed system rust will start but will be limited to the amount of oxygen available within the water in the system, if no new water enters the system rust will stop completely. The rust coverters I've tried didn't do much IMO. I have epoxied over surfaces with pitting containing rust and have found it holds up extremely well. A crude example: My Dad had me prime and paint a tube bumper he had made, pitted all to hell and it was already mounted on his truck so sandblasting wasn't considered. Layed on 4 coats of DP40 primer followed by 3 coats of Concept singlestage urethane. That was 14 years ago and the bumper still looks great. At the time I thought the paint wouldn't last a year! Ramble, ramble

I used Nason's etch primer and applied their 2k Urethane primer. I plan on blocking this and then applying my primer sealer and then base coat. The guy at the paint store said that the urethane is like epoxy primer in that it seals good enough to keep moisture out permanently and that it is a high-build primer.

I figured that the problems I hear about etch primer are related to misuse or the use of non-compatable primers over it. I have always heard if you have bare metal spots then etch is the way to go and now after I did that I hear about problems with it, lol.