How to Get Rust Stains out of Clothes
To get rust stains out of white or unbleached fabric, liberally sprinkle the stained area with salt, then cover the stain with either lemon juice or vinegar. Allow the mixture to soak into the stain for about 5-10 minutes, then blot the stain with a clean white towel. Place the garment outside in the sun under a towel for about 3 hours or until it has dried, checking every hour or so to make sure the lemon juice doesn't bleach your fabric. After the 3 hours, rinse the fabric with cold water, then wash it as normal.
Purchase a commercial rust stain remover. You can check your local grocery store, home improvement store, hardware store, or an online supplier for rust stain removers to select from. You will be able to find them in the laundry aisle at supermarkets or the home goods section. Apply rust remover to the stain. You should use just enough to fully cover the stain, however big it may be. You may let it sit in the material for a few minutes if necessary. Carefully read any directions or warnings prior to application as it may tell you the exact measurement or time to leave on the material. Rinse and rinse again. You'll want to give your clothes a thorough rinse with clean, cold water. A second rinse will remove the harmful acids that may linger and deteriorate the material of your clothes. Then, launder your clothes as normal. The main component in rust removers is an acid that will lift the rust stain from your clothes. Acids present in commercial rust removers such as oxalic or hydrofluoric acid will cause damage to skin and household appliances. Cover the stain with lemon and salt. Liberally sprinkle the stained area with salt. Afterwards, fully saturate only the stain with lemon juice. This process is safe for white or unbleached fabrics such as linen. Colored or delicate fabrics such as rayon, silk, wool, leather, and suede are to be taken to a dry cleaner. You may also substitute lemon juice with white vinegar. Vinegar is a good choice if the stain has been present for some time. Soak and blot the stain. Allow it to sit for about five to ten minutes. Blot stain with a clean white towel. Dry the spot in the sun. After thoroughly coating the stain with the salt and lemon juice, place material outside in the sun under a towel until dry. It is recommended to check every hour to make sure the lemon doesn't bleach your fabric for up to three hours or until the stain has faded. To finish, give it a good rinse with cold water before washing as normal, since lemon may leave a stain or bleach light clothing. If sunlight is not available you can also simply air dry until the spot is completely dry! Boil the rhubarb. Get a pot that is large enough to contain the stained clothing article. Fill it halfway to three-quarters with water and add rhubarb stalks. Bring water to a boil for 20 minutes. Unlike lemon and salt, rhubarb is not as well known for removing rust stains, but it's gentle on fabric and will safely remove the stain. Rhubarb, a plant whose stalks which are used mostly for food and medicine, is known to be a natural mordant, which is what allows dyes to bind to fabrics so that dyes don't fade too quickly. However, it does not dye fabrics on its own. Soak the stained garment in water. After removing the pot from the heat, take out the rhubarb. Soak for a few hours or until the stain is no longer visible. Wash as normal. Carefully inspect that the rust discoloration is completely gone. If so, rinse thoroughly before laundering. 
Purchase a commercial rust stain remover. Apply rust remover to the stain. Rinse and rinse again. Cover the stain with lemon and salt. Soak and blot the stain. Dry the spot in the sun. Boil the rhubarb. Soak the stained garment in water. Wash as normal. 