While the process of removing rust from a washer tub is fairly straightforward, it requires a nearly infinite amount of patience. Washer tubs are full of holes, and often the rust has formed inside these tiny holes, making it very difficult to eliminate. However, if your clothes are showing signs of rust and you are not in a position to purchase a new washer, you can attack rust from a washer tub and remove a large part of it, if not all of it, thereby alleviating or solving the problem at least for the time being.
Attack visible rust with a baking soda cleaning combination. Combine a cup of baking soda, half a cup of salt and a tablespoon of vinegar in a small bowl. Add lemon juice until a paste forms that can be spread but that will not run. Expect some fizzing. Spread this paste across the interior of the washer tub, covering all visible rust. Leave the paste on the rust for 15 minutes before scrubbing it off with the plastic-bristled brush. Make sure as you scrub that the bristles are going into the tiny holes in the sides of the tub to get as much rust out as possible.
Rinse the interior of the tub. You can pour water into the tub and then wipe down the sides with a damp rag. This will enable you to see how much you have accomplished. You can repeat the baking soda treatment four or five times if the stains are lightening but have not yet disappeared.
Run the washer while it's empty using the commercial rust remover. These removers are designed to get rust stains out of clothing. Make sure that your rust remover contains oxalic acid, which will dissolve rust in many cases. It is also called "wood bleach." Follow the manufacturer's instructions for a full load even though your washer is empty.
Scrub down the interior of the washer tub. Wear gloves in case any of the rust remover is still in the tub. Use some baking soda and the plastic-bristled scrub brush you used earlier. Any rust that the commercial remover did not dissolve may have at least been loosened, and you may be able to get it off by hand.
Run the washer on hot with 2 tablespoons of Tang powdered citrus drink. The citric acid in the drink will further attack rust and prevent the formation of more rust. Do not put anything in the washer, but set it as if it contained a full load.
Wash out your washer tub. Run your washer on hot with regular laundry detergent to get all the cleaning agents' residue out of the washer tub.
Wipe down your washer tub with a clean rag. This will pick up any remaining residue and any rust flakes that may not have washed down the drain.