You have a few choices:
-- Take it out of Earth's atmosphere.
-- Put it in a tank where you pumped all the air out of it.
You can put whatever you want back in the tank, just
as long as there's no oxygen in there.
-- Besides oxygen, rusting also needs water. The humidity
(water vapor) in the air is enough to do it. So if you can
keep the air totally, totally dry around the iron, then the
oxygen alone won't make it rust.
-- All these choices do the same thing: Make sure that
oxygen and water vapor can't reach the iron. The easy
way to do that is to paint or spray something onto the
surface of the iron that keeps the air away from it.
