metal roof paint

I found someone willing to paint the 7/12 pitch, 40 year old galv. metal roof on my shop. It has about 20% surface rust.

What kind of paint?

Around here folks on farms use an aluminum roofing paint, such as this product from a local distributor.

https://www.agrisupply.com/roof-pain...paint/p/21246/

Rust should be removed by scraping and wire brush, and the metal roof cleaned thoroughly with soap and water. Some locals even will do a vinegar wash.

A rust converting primer on the rusty areas would not be a bad idea.

I'd go to a Sherwin Williams paint store and find out what sort of primer they have for galvanized steel.
Alkyd oil primers are not recommended since the alkyd resins and the zinc used in the galvanize process interact to form a soap (saponification).


Now - having said that - the odd thing is that nearly all of the (oil based) galvanized steel primers for old weathered surfaces are - - alkyd oil based.
Go figure..

I just did mine last year. It was probably more like 75% rust. Started with Rustoleum rusty metal primer, after a good washdown, then a coat of Rustoleum bright white.
So far, so good. When it next needs it I'll probably just go with an aluminum colored paint sold by the local farm store since I won't let it get to the rust stage again.

I have to go to Nevada to buy the aluminum fibered roof coating. Take it to the paint department and have them shake it up for you. Use it in a day or two or spend 20 minutes per can mixing the flakes off the bottom.
Bill D