One of the tubs in our new home has a few spots where the enamel is chipped away and the metal underneath has started rusting. I don't want to replace the tub yet, so how can I clean and patch the tub? Not so much concerned with aesthetics as with prolonging the life of the tub.
With one of these: Enamel Repair Kit
You simply sand out any rust in the chipped enamel, then paint on a new enamel coating. The finished repair should be permanent, and if well-done nearly undetectable.