Grain bins with rusty metal

[Covert Operator]

I'm looking at a couple of different used cone-bottom grain bins. They are galvanized metal, with some rusty surfaces from wear and moisture inside.

If I grind/sand/buff away the rust down to smooth shiny metal, what sort of finish/paint/coating would be recommended?

[Moonlight]

Inside the bin I would use nothing. There shouldn't be additional rust forming if it stays dry, and the grain may just scrape any coating off into your beer regardless.
Don't forget breathing filtration while working in there!
Spoken from experience...