The moisture mixes with oxygen and forms rust.
Removing rust from door hinges without removing.
But it is important to seal the metal away from moister as soon as you can.
In addition to its unsightly appearance rust can corrode and weaken the structure of metal causing holes to appear and increasing the possibility of the hinge breaking or snapping when the door opens.
Scrub the hinges with a medium bristled brush.
Scrub off all the dirt debris and rust you possibly can.
If you still have a lot of rust i would let them soak more.
With any rust removing method it will take some patience and some elbow grease to remove the rust.
At this point they looked clean enough to be removed from the mixture.
You can remove rust using household ingredients such as aluminum foil and a mild acid like white vinegar or with special rust removing chemicals.
Rust accumulates on door hinges when moisture is allowed to build up on the surface of the metal.
I was refinishing a bathroom vanity cabinet but the hinges had rust on them so i needed to remove the rust before reusing the hardware.
If rust is still present try using steel wool on the metal parts.
You cannot use steel wool on brass plated hinges however or you may ruin them.
I waited several hours and by the time i came back to them vinegar baking soda mixture was orange with rust and a lot of the rust had been removed from the hinges.
Vinegar and a steel wool pad or naval jelly follow directions will remove the rust.