The iron cylinders will rust over time. It wasn't an issue for me since I planned a total tear-down from the beginning of my project, so I was able to sand-blast and repaint very easily.
How bad is the rust? Can you post a picture? If it's minor (reachable), you should be able to clean the rust with a small wire brush and hand-paint the cylinder with a thin coat of engine paint.
My original cylinder is at the left below.
