Wink Brand rust remover, if you can wash it in a large commercial front load washer.
If it’s dry clean only, then you’ll have to find a dry cleaner that specializes in fabric restoration services.
If you insist on washing a dry-clean-only product yourself, it must be washed in cold water and line dried to prevent shrinking. Even then, if any of its rayon, rayon typically wrinkles and shrinks when washed.
TRy vinegar on the stain let it soak on spots rinse cold
IRON OUT--Make a paste. Many department stores carry a cleaning product that is called Iron Out, which you can use to help remove rust stains from cotton. This cleaning product usually comes in a powder form, so you will need to make a paste out of it. Apply the paste to the stained area, and allow it to dry out. Gently scrub and rinse the paste away, and you should notice that the stain is dissolved as well.
CLR will work. CLR Calcium, Lime, and Rust Remover) is a product that is surprisingly gentle and effective at removing things like rust stains. Simply soak the stained cotton fabric in some CLR for a few minutes, and then remove. Once you have removed the stained fabric from the CLR wash it as you normally would.
For white cotton only. Use a little bit of Dawn, or Plain Palmolive dish detergent, CLR and warm water to wash the rust stains away. On the average you will only need to use six cups of warm water, one shot glass of detergent, and one shot glass of CLR. Be sure that you are wearing some rubber gloves, and begin hand washing the stains away. The rubber gloves will help protect your hands from the CLR, and allow you to get a better grip on the material while you are washing it. After you have rinsed the material until you only see clear water, soak it in a solution that is 50% warm water and 50% hydrogen peroxide for 30 minutes. Rinse well after that time has passed. Now, wash the material as you normally would in the laundry. Dry the cotton outside if you are able too. If you use this method on any cotton fabric that has colors, be aware that those colors will fade.
If all else fails----Chemicals can help. Many higher end camera shops carry some chemicals that you can purchase to develop your own photographs, or if you are creative, use to help remove rust stains from cotton. You can use one of two chemicals to help remove iron (rust) stains from cotton. These two chemicals are called sodium thiosulfate, and potassium thiosulfate. Simply add a teaspoon full of the chemical to a glass of water, and stir until it has dissolved. Soak the cotton fabric in the solution for several minutes, and the rust will slowly fade away. Rinse the fabric clean in water.