Welcome Manzie.
Having been at the top of the tower on a lightship when the horn was set off, I would suggest just operating it, and all the rust will evaporate into rust!
A wire brush followed by a brush on gel rust remover or converter would be a good start for a big sheet metal object, Jenolite Rust Converter might be a good place to start.
Bronze or gunmetal ones must be fairly small, a Trinity House one of bronze would cost a small fortune!
Neil