Jonathan Hatch
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How to Get Rid of Rust Stains
Have you been working in your yard, on your boat, or around your house, minding your own business when suddenly a rusty nail comes out of nowhere and leaves a stain on your new white shirt? I've been there, and getting rust stains out of cotton and other fabrics is an exercise in patience. So I did some research on the subject and here's what I found out:
Removing Rust Stains from Fabric
Cleaning rust out of fabric is most often done with a type of acid, usually because rust (oxidizing metal) becomes water soluable when acid is applied to it. But before you clean anything with an acid, it's a good idea to test it on an inconspicuous piece of the clothing first--just in case it starts burning a hole in your favorite shirt. That being said, here are some of the typical acids and treatments that are used to take rust stains out of fabrics.
Citric Acid, an acid found in fruit, is a mild and effective rust removing agent. Don't just run out to the store and buy a bunch of oranges though. You need to have a somewhat concentrated solution. I believe Lysol makes a citric acid cleaning solvent, and it's fairly mild--so they say.
Acetic Acid, a mild acid found in vinegars, is also a good rust remover. Get a bottle of regular white vinegar at your local grocery store and dab at the stained piece of fabric. Rinse after doing this, and see if the stain is gone. If not, repeat the process.
CLR, a common bathroom cleaning solution, is yet another way to remove rust stains. Simply squirt a little of the solvent onto a rag and dab at the stain. But BE CAREFUL, this shouldn't be used on delicate fabrics. CLR is a very strong rust removing chemical. It might not be wise to use this on delicate things, like your wife's new bikini or your husband's new thong. 
Oxalic Acid, the acid found in products like Bar Keeper's Friend, is a strong acid that is used to clean rust off of decks, cars, and other heavy appliances. Be very careful if you plan to use this acid on clothing. Diluting the substance with water might be a good idea before using it on delicate fabrics.
Cream of Tartar is a good rust removing agent. Though it is most often used in baking and other culinary practices, it is the acidic potassium salts in cream of tartar (tartaric acid) that does the rust moving. Make a paste of it, slap it on, let it sit for a while and then rinse.
Stain Removal: Chemicals & Treatments
If none of these solutions have helped, there are always the ubiquitous rust removing agents and solvents found in your local drug or grocery store. There are also a number of different rust and stain removing solutions offered online; many of them are gimmicky solutions that tend to bank on the reaction between acids and rust. But hell, if the price is right, go for it. Just do a little research before you dump a lot of money into a product that doesn't work.
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