Stains bleeding through paint

[Chris Jones]

I'm painting my cast iron fire hydrant top and caps white (spray paint / rattle cans). Basically all the original paint has been removed but where a tiny bit of the red paint remains around the head of a bolt or in the cast letters and it bleed through the primer and two coats of white. It looks like someone took a red ball point pen and ran it around the bolt heads and downside some of the letters. I can't get the old paint removed any better, frankly it's hard to tell it's there. I've washed off the white with mineral spirits and pretty much confirmed the pink is showing up where tiny spots of the old paint remain. I need to start again. I've been given advise from two folks so far. 1 - Use a darker primer (the primer I used was white and I was advised to use grey). 2 - Use aluminum paint (I think there is a paint with aluminum in it but Ace Hardware didn't have it and I'm not sure what I'm looking for).

Any suggestions on primer or paint that will not allow bleed through?
 

[Uncle Ernie]

Strip the old paint with oven cleaner. Works swell. Then prime it with KillZ.
 

[El Toro]

You may be better off to wait until all that paint hardens and then start over by sandblasting
all the paint off. If you don't have a spray gun
I would get a body shop to paint it. I would start with an epoxy primer. Hal
 

[big fred]

To remove the original paint, did you use stripper? If so, I'd guess the bleed-thru areas are where you didn't wash off all the stripper or there are remaining bits of paint that are still reacting with the stripper. Otherwise a sealing primer (from autobody shop) should take care of it.
 

[circus]

Scuff and coat with killz sealer then repaint the area
 

[Stephen Newell]

If the fire hydrant is going to be used outdoors then Kilz shouldn't be used. Its a interior primer. For interior use the Kilz Original can be used on bare metal but it shouldn't be used over rattle can paint. If it were me I would just let the paint you are using cure for two weeks and just spray it white again. Just don't put a thick wet coat over it or the toluene in the rattle can paint will bring out the red again. It will eventually cover, you just have to let the paint cure good between coats.
 

[cd1]

This is why primer/sealers are for. Try an autobody paint supplier. Check the yellow pages.
 

[Uncle Ernie]

KILZ® GENERAL PURPOSE EXTERIOR is a fast-drying latex primer and sealer, specifically formulated for outdoor use. It minimizes problems caused by surface texture and porosity differences. It’s ready to brush, roll or spray and can be topcoated after one hour with latex or oil-based paint.

Surface prep is still the most important step. Strip that sucker bare and clean it dry first...
 

[Stephen Newell]

The problem is the Kilz exterior primer is intended for use on porous surfaces, not steel or cast iron or over rattle can paint. Also if the fire hydrant was sandblasted down to bare metal using a latex product you would have trouble with rust bleading through the paint.