Primer questions

[stopwatch]

I have sanded my car down, I have a lot of bare metal and have treated the rust with POR-15. I was planning on taking my time while restoring it but I just got orders to move to Hawaii from Virginia... I don't have time to paint the car right, nor am I done with all the exterior work, so my two questions are...

What is the best primer to use on the car to protect all the work I have done? Self etching, POR-15 "special primer", epoxy, or a K-mart brand?

Can I paint the car with epoxy primer and put no topcoat on it for several months and expose it to the weather with little chance of having to sand it all the way down again?

Thanks for any insite!

[MagicRat]

POR-15 is not the best thing to treat rust with, if you are going to use proper paint on it later. Rust needs to be removed entirely, not just covered up.
You are better to blast (sand, baking soda, walnut shells, etc) the rust spots, (or grind them), treat them with phosphoric acid, then prime them.

But thats a different story.

Primer is only useful for cars left in a clean and dry garage. Most home garages are not dry enough, they are subject to condensation and moisture, especially in the spring and fall.

Primer generally does not seal out weather and moisture. It is intended to be used as a prep coat only for the final coat. A car left in primer will rust relatively quickly if exposed to moisture.

If you are to leave this car in a moist area, just buy some basic primer, spray it and then use a top coat of cheapo enamel. It will protect the metal from rust. Chances are, you still have some sanding and filling to do on the body. This cheap paint will be a good 'guide coat' for sanding, when it comes time to prep the area properly.

[stopwatch]

Well since the car will be in the weather, and just the primer won't protect the car, what's your thoughts on one of the 199.00 paint jobs. I know they don't use a primer, but it "should" protect from rust for several months I would "think", what do you think about that?

I apprecaite your insite this and on the rust/por15...

[Racincc85]

crap.....looks like im going to have to sand down and retreat the rust spots on my car that i left in primer when i get back home in two weeks. I bought a car in the middle of march but i had to go back to iowa for two months and didn't have time to fully paint it, so i just left a few spots in primer and threw it in my garage. How bad do you think it'll have rusted? I'm not really looking forward to getting back to work on it now....

[curtis73]

I'm not a body man, but rust itself needs to be removed or treated. Just sealing it doesn't work. Rust comes in two forms; Fe2O3 and FeO2. The second kind with two oxygens is the fast rust that happens quickly and is typically orange in color... like when rain falls on fresh bare steel. The first kind is the flaky darker stuff and it can form without exposure to air. Sealing it off does no good. Several FeO2 molecules can come together and give its extra oxygen to new iron atoms. Even if you seal it off, rust grows on its own. Hence one of the reasons its called cancer.

Either remove it entirely or treat it with an acid to turn it into something else so it doesn't grow.

I was also told that primer is (by nature) porous and doesn't seal out the environment. Just priming the car won't necessarily prevent new rust from forming since air and water can get through the primer to the metal.

Again, take my words with a grain of salt since the only body work I do is at the gym

[astroracer]

A good 2 part epoxy primer will seal bare metal for a short time when left out in the elements. It is not UV stable though so it will break down when left in the sunlight. Talk to your paint supplier and get his recommendation.
Mark

[Racincc85]

I originally used phosphoric acid to dissolve the rust before i primed it. I put on liberal amounts and let it sit overnight. The next day i primed it with some primer that contained zinc and was supposed to help prevent the formation of new rust. The spots were each about the size of a quarter. The car's been stored in my garage for about 6 weeks, so at least it hasn't been directly exposed to any of the elements. I'll probably sand down all the primer when i get back home in two weeks, treat it again with phosphoric acid then put enamel on it right away. I'd rather take the time to do it right then have the rust come back on me in two months. For good measure i'll probably use a heat gun on the bare metal before priming it to make sure all the moisture is gone, then do the same on the primer once it dries. Thanks for the advice!!