Galvanized Roof Rust

The roofs i have done have lasted a minimum of 20 years now.

Galvanized roof rust.

If you are preparing to paint a rusted galvanized metal roof pay special attention to surface preparation or you will have a recurrence of rust and or flaking. But galvanized metal which exhibits a shiny adherent but rust colored stain is not truly rusting. Most metal roofing is made of galvanized metal or coated to prevent rust from occurring but standing water and the heat generated by direct sunlight can wear the roof s protection away. Galvanized metal roofs are coated with a layer of zinc that inhibits rust.

It is not simply a cosmetic problem however. Galvanized metal is coated with a layer of zinc to protect the iron or steel underneath. Left untreated white rust corrodes the zinc and the metal underneath begins to rust exhibiting the more traditional brownish red color. I like the fiber in the aluminized roof coat as well as in the black nearly tar roof coat.

Rather this is just a phenomenon that often occurs in galvanized materials due to intermetallic alloying of iron and zinc i understand and is not indicative of the end of the useful life of the galvanizing. I have used both regular paint and roof coat on old metal roofing with pretty good results. Rust is the reaction of oxygen moisture and metal that results in reddish brown blotches. The fiber acts a bit like a tire plug in the old nail holes and prevents leaks and it sticks well.