Over time, the elements of nature can quickly wear on a metal door. Rain, wind and snow damage will begin eat away at the protective surface layers as visible amounts of rust will spread. Removing the rust and preventing further damage is the homeowner's only defense from having to completely replace a metal door.
Pour the vinegar on the patch of rust on the door. Let the vinegar sit for one hour, or at least until the rust begins to dissolve.
Dip the thick-bristled scrub brush in fresh, clean water and scrub away the vinegar and rust. Repeat with more vinegar for a longer sitting period if there is resistant rust.
Blend together baking soda and clear water into a thick paste for stubborn rust. Apply the paste on the rusted area of the metal door and let it dry over one to two hours.
Dip the hand towel in fresh clean water, then wipe away the baking soda paste. Repeat for deep rust spots.