New answers tagged rust-removal
It turns out that this was rust. The flashings above this window (around the deck above had significant rust. We ended up reconstructing a large section of this to deal with the issue.
It is difficult to find a "rusty metal primer" which is intended to take a latex paint topcoat. The Rust-Oleum product shown recommends an oil-based top coat which should not be used when repainting a metal garage door. An alternate product might be Corroseal which is a rust converter and latex primer in one which can then be topcoated with a latex paint.
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