Removing rust stains from clothing using home remedies is tricky--you may have to use trial and error or repeat applications until your rust stain is gone. Most of the available home remedies have been around for many years and there are many people who swear by them. You can try any of these following techniques and, if one of them does not work, try another one.
Chemical Vs. Natural
The most effective way to remove rust stains from clothing is with hydrofluoric acid or oxalic acid, which are found in commercial brands of rust removers. Hydrofluoric acid is difficult and dangerous to work with and is not usually just lying around the house but you do have other acids in your home that can be effective. You will need an acid that is safe to use and not as toxic. One thing to remember is never use chlorine bleach on a rust stain: This will not work and will only set the stain permanently.
The most popular method is using a combination of lemon juice and salt. Sprinkle salt on the rust stain then add a few drops of lemon juice, lay your garment out in the sun until you see it fade away. This remedy should be spot-tested first when being used on colored fabrics to test their colorfastness. You can also substitute the lemon juice for white vinegar and use a toothbrush to apply. Use the vinegar if you are having trouble with colored fabrics or the lemon juice method does not work; there is no need to place it out in the sun. Another remedy to try is cream of tartar; add the spice directly to the stain, using a rubber band make a bubble or pouch filled with the spice then dip it into very hot water for 10 minutes. Next you can try Coca-Cola, everyone has heard about its ability to clean corrosive battery acid. Soak an abrasive sponge with the soft drink, scrub until the rust stain disappears. One more option is to boil four or five rhubarb stalks in water, after it has come to rolling boil let the mixture cool for 15 minutes, then strain. Put you rust-stained clothing in the water to soak for at least two hours, check to see whether the stain is still there. If needed, you can leave the garment in the water overnight. When you are done with any of these methods and your stain is gone, wash your clothing as usual. You can reapply any of these methods as much as needed until the stain is gone.
The University of Iowa has an excellent sheet on removing any type of stain from any type of fabric. Always check colorfastness when using home remedies by applying a tiny amount of the solution on an inconspicuous part of your garment like the underside of a hem. Never scrub a rust stain vigorously, but gently pat and blot the solution onto the stain, unless otherwise directed.