What exactly are the parts made of, and/or coated with, to begin with? If they are bare steel, they are going to rust no matter what, unless you put some sort of protective coating on them. Paint, chrome, clear coat, etc. If the pieces are what looks like bare steel, chances are they had some sort of clear coating on them to start out that is gone now. If they are chrome plated and were rusty, the rust will keep coming back from the pits in the chrome surface that go down to bare steel. You can slow that down, but it is hard to stop it. Steel and moisture don't go well together, so you need to somehow separate the two.