If you are meaning the "barrel" of the iron, it has no effect on the iron. It gets rusty due to the fact that it was plated just to entice you to buy it. It wasn't made to stay that way, like the 'chrome' on your car.I have one of these dirt cheap soldering irons:
But I've noticed that over time the heater body gets kind of rusty(not the tip). How do I prevent it? Is there any way to keep it shiny?