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Stain coming through paint

Posted by criticalmass (My Page) on
Mon, Nov 5, 07 at 11:51

I am renovating my apartment, which was built in the early '60s I believe. This place has metal doorframes on all the interior doors, similar to an office. It's already a pain in the neck, because the hinges can't be replaced (one half is molded into the frame somehow) and the striker jam (I think that's the right name) is pre-cut into the frame, which has settled over time so a lot of the doors didn't shut properly. But that's not my problem.

On three different doorways, I used a heat gun to get rid of the layers of paint caked on the frame. When cool, I then sanded the frame, primed, and painted with two coats.

The next day, I noticed tiny brown spots on one frame. The best way I can describe it, it looks like something was splattered on the frame, like Coke or blood or something. They range in size from pinhole, to about half the size of a pencil eraser. I found this strange, because I knew it was not possible. The surface was also still smooth. So I put a little paint over the area again, and still, the stains are coming through.

I used the same brushes, primer, and paint on two other doorframes in the house at the same time, and the other two don't have a problem. This one, however, is right next to front window, so is exposed to sunlight. Could this have something to do with it? I just find it hard to believe that even rust would come through that fast.

Thanks!


Follow-Up Postings:

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RE: Stain coming through paint

It very well could be rust finally rearing it's ugly head.Being by a window, it could be moisture build up from the sun coming in causing condensation behind the jamb. As it has rusted, the rust is now surfacing.Rust never sleeps!


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RE: Stain coming through paint

But as I said, I sanded it down to the bare metal. I saw no obvious signs of rust. And would it be strong enough to come through one coat of primer and two coats of paint in 24 hours??


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RE: Stain coming through paint

Sorry, i misread your post. I dont think it would appear that fast either.On that particular jamb, did you notice anything different after sanding? By different i mean things like the surface of the metal being coarse and even slightly pitted compared to the others.If rust had been protruding, i think you would have spotted it when sanding.A coarse, pitted surface after the sand could indicate rust, but i think you would have caught it. One of those scratch your head situations that make diy'ers head for the mental ward! Im on the fourth floor room 1a!Sorry i couldn't help. You sanded to bare metal, primered and finish coated twice. I have no clue.

Maybe brickeye has an idea.Brickeye, you got a copy?


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RE: Stain coming through paint

What kind of primer did you use?


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RE: Stain coming through paint

If you paint over rust without using the proper primer for rust or a rust converter, then yes it will bleed through almost right away. It may be that you sanded beyond the original metal primer in some areas?


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RE: Stain coming through paint

If you paint over bare steel with latex products the rust spots can easily appear in 24 hours.
Use an alkyd product for at least the primer, and preferavly all the coats of paint.
Rust Oleum or some other brand.
If it cleans up with water it is NOT acceptable.
Look for a primer that cleans with paint thinner.

Even after using an oil (alkyd) primer, latex paint is not a good finish.
Painting is rarely perfect enough to completely seal the surface.
The water in latex paint will cause rust if there are ANY defects in the primer coating.


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RE: Stain coming through paint

Thank you all for the good replies.
OK, so now that I was stupid enough to try to put latex paint over the metal, which is the correct solution?

1) Scrape off and sand everything back down to the bare metal, and start from scratch with the appropriate primer/paint.

2) Leave what's there, and just go over it with appropriate paint

3) Leave what's there, and just go over it with appropriate PRIMER & paint


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RE: Stain coming through paint

Of course if you use the RIGHT latex product over the metal, you will have better results.

This is 2007. You can use latex products over metal as long as they are formulated for that purpose.

Benjamin Moore IronClad Latex will fix you up.

Michael

Here is a link that might be useful: Latex over metal is an everyday thing


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RE: Stain coming through paint

You can go over it with oil based paint but then it won't match the rest of the trim painted with latex.

I would hit it with a coat of Kilz and then top coat again with the latex. I don't think you need to go to the extreme of stripping, rustoleum cleam metal primer (twice), then topcoating with latex.

I've had it with oil based interior topcoats, the finish is the best there is but they have always yellowed on me. I don't know how they can put "Non-yellowing" on the label.


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RE: Stain coming through paint

Kilz doesn't work on rust.


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