Galvanized Roof Rust

Rust is the reaction of oxygen moisture and metal that results in reddish brown blotches.

Galvanized roof rust.

It is not simply a cosmetic problem however. But galvanized metal which exhibits a shiny adherent but rust colored stain is not truly rusting. The fiber acts a bit like a tire plug in the old nail holes and prevents leaks and it sticks well. If the item is exposed to continually wet conditions the zinc develops a film known as white rust.

I have used both regular paint and roof coat on old metal roofing with pretty good results. Left untreated white rust corrodes the zinc and the metal underneath begins to rust exhibiting the more traditional brownish red color. 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. Rust corrodes metal and if left untreated it can cause.

I like the fiber in the aluminized roof coat as well as in the black nearly tar roof coat. Unfortunately over time this coating can fail leading to minor rust outbreaks. 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. Galvanized metal roofs are coated with a layer of zinc that inhibits rust.