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Best coating for rust-stained galvanized roof?
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I have a question about galvanized metal... what are the best coatings for galvanized roofs (corn cribs) that have rust stains on them?
Arthur BrownPainting by Brown's
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The first question is whether they are *really* rusting or not. A powdery, scrapeable, dust, with corrosion pits below is indeed indicative of true rust. But areas which exhibit a shiny, adherent, brown, rust-colored stain are not truly rusting! Rather, this is just a phenomenon that often occurs in galvanized materials (due to intermetallic alloying I guess), and is not indicative of the end of the useful life of the coating.
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We live in Hawaii and are planning to repaint our galvanized roof. Do we need to prime the whole roof before painting or do we prime only the rusty areas?
gerri kahili- Hawaii
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Hi, Gerri. Getting good adhesion to galvanized surfaces is notoriously hard, so you must prime the entire roof with Self-Etching Primer [linked by editor to product info at Amazon] for galvanized surfaces. Regards,
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"Rust Restorers"? My question is, do they work and if so how do they work? I have used one type in particular called Extend on my truck to try to stop some small rust spots from getting out of control and it apparently works because they have not spread since the application 3 years ago.("RUSTOLEUM" makes a similar product) I was also curious to know if there are any similar products used to coat rusted areas of galvanized roofing prior to refinishing or painting to keep the rust from resurfacing? Kevin Mott- Newport Rhode Islandaff |
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I have wondered what kind of paint do I need to paint my galvanized steel roof. Where can I buy the paint.
RANDY BUI- BERLIN, MARYLAND
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Hi, Randy. Unfortunately your question is just a bit vague, because we don't know the age of the roof or why you are painting it. If it's quite old and rusty, any primer for metal, followed by any outdoor paint designed for metal is probably okay, although a Rust Converter [linked by editor to product info at Amazon] might be a good idea. If it's a newer roof, the galvanizing can definitely cause you adhesion problems. Scrub with trisodium phosphate [linked by editor to product info at Amazon], then use a Self-Etching Primer [linked by editor to product info at Amazon] for galvanized surfaces. Good luck.
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September 25, 2010
I am a student and we have an experiment on finding ways on what to do with a very old and rusty galvanized roof. other than applying a primer and painting it, are there other ways?
Shammy Lorenzo- Manila, Philippines
September 27, 2010
Hi, Shammy
I don't quite understand your experiment, but if you are looking for theoretical ways to extend the life of the roof: you could bolts blocks of zinc to it as is done with ships, or you could apply a voltage to make the roof cathodic with respect to something.
Regards,
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |