According to the magazine ‘This Old House” Nov.Dec. Issue 2013, they suggest that you should pick up a pumice stick-the kind with a handle designed for cleaning toilet bowls-to remove those rusty stains without scratching your porcelain. Soak the pumice stone in warm water for a minute, then start scrubbing gently. To prevent scratches to the porcelain, keep the serface and the stone wet; also, steer clear of metal fitting that can be damaged. If you do have damaged metal fittings they can be easily repaced as well.