Best coating for rust-stained galvanized roof?

---

I have a question about galvanized metal... what are the best coatings for galvanized roofs (corn cribs) that have rust stains on them?

Arthur Brown
Painting by Brown's

---

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.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

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

Hi, Gerri. Getting good adhesion to galvanized surfaces is notoriously hard, so you must prime the entire roof with Self-Etching Primer [link is to product info at Amazon] for galvanized surfaces.

Regards,

Ted Mooney
finishing.com
Brick, New Jersey

"Rust Restorers"? My question is, do they work and if so how do they work?

I have used one type in particular called Extend [link is to product info at Amazon] 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 RI

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

Unfortunately your question is a bit vague, Randy, because you have not indicated 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.

If it's a new roof the galvanizing can definitely cause you adhesion problems. Scrub with Trisodium Phosphate [link is to product info at Amazon], then use a self-etch primer for galvanized surfaces. Good luck.

Ted Mooney
finishing.com
Brick, New Jersey