in vinegar overnight and then scrape the rust away in the morning.
it's best to use apple cider vinegar instead of white vinegar. while white vinegar may work, it's not as effective as apple cider vinegar.
although vinegar is effective, it is also relatively mild. you may need to soak the item for longer than overnight; a day might be best. after removing the rusted item from the vinegar, dip a crumpled-up ball of aluminum foil into more vinegar and scrape away at the rust.
use lemon or lime juice. lemon or lime juice works particularly well for rust stains on clothing, but it can also be effective on metal if left to 