Remove rust from old metal fixtures.
Place fixture in the kitchen sink or large bowl. Pour white or apple cider vinegar that is 5% acidity into the sink with the fixtures. Put some ketchup in with the vinegar. Let the fixtures soak for a few hours. Wearing gloves, take each fixture and put some extra ketchup on them and scrub them using an old tooth brush. After scrubbing each fixture, place them back in the vinegar solution and let them rest a few more hours. Scrub more if necessary. Remove from vinegar solution, rinse off with water, and immediately dry with a cloth or paper towel afterwards. If you don't dry them they will oxidize again with the water and create more rust.