I can practiacally guarantee they are aluminum and not steel. I would get some DTM. (direct to metal) it comes in oil or waterborne. Give it a little scuff, and wipe, and put it on. Honestly, I would probably skip the scuff, but its better to just do it. If its rusty (which it shouldnt be) you'll want to nuetralize the rust before paint.
They make primers for DTM, but its unusual that they be necessary. probably for going on galvanized surfaces or something.
If a roofer suggests something else, look into it. Ive never heard of tinning paint. The only thing Ive come up with on google is about soldering... It might be for raw metal or raw tin.. Just because roofers use it, doesnt necessarily mean its better... Maybe it is though, idk. Ive done a lot of exterior repaints, and Ive never seen factory painted metal on a roof that was in good shape. I'd personally trust DTM over what Ive seen them painted with. Youre also not going on raw tin, your going on top of an existing paint layer.
DTM WILL work though, if you cant find this stuff.
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