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How do you repair surface rust on tin roof? Answered

I stacked some galvanized tin roofing sheets outside. Water got trapped between the sheets. This resulted in surface rust and some oxidation. The sheets are20 ft long. The damage covers about 15% to 20% of all the surface combined. Is there a product that I can use to repair the damage?



Surface rust is oxidation, and there's no tin in these things. The zinc coating (galvanised) is supposed to prevent rusting, but it only lasts until the zinc has oxidised. Do as Gorfram suggests or consider replacing the sheets.


The primary product you need is Elbow Grease. Doesn't cost much, but it takes some effort to apply properly. :) What you need to do is to get all the rust off of the sheets. All of it. Wash or sweep down each sheet to remove loose rust. Then scrub it with a nylon-bristled brush, and finally with a metal brush. Once you've removed every last particle of rust, repaint the sheet with a rust-preventing primer (Rustoleum or something similar). Then paint on at least 2 coats of a roofing paint compatible with the primer. Rust is sort of like cancer: if you leave even one tiny iota, it will grow back. Wherever the paint sticks to a tiny little bit of rust instead of to the roof material itself, the water can get in under that little hole in the paint. That will rust the steel all around the hole, and new rust will form underneath the paint, pushing it paint away from the metal. Then the cycle repeats itself, getting bigger all the time. (That's how rust works, anyway - I've got no clue how cancer works.)