Rust can leave a very unsightly reddish-brown stain which can be difficult to remove. If you find rust stains on clothing, first of all make sure that you do not put the garments in the dryer or iron them before treating the stains. Heat may set the stains permanently and make them impossible to remove. Also, never use chlorine bleach as this will set the stain as well. One of the best solutions for rust stains on clothing is lemon juice (citric acid) or the stronger white vinegar (acetic acid). Both of these are mild acids which will help dissolve the iron oxide compound. Place some absorbent white paper towels beneath the stain to act as a blotter, then cut a lemon in half and soak the stain with fresh lemon juice (alternatively, bottled lemon juice will also work). Leave the garment (with the paper towel blotter still beneath the stain) out in the sun to dry and the rust stain should gradually disappear. Wash according to the usual instructions. You can also launder the stained clothing with commercial rust removers - these will also contain acids, usually oxalic or hydrofluoric acid - which will combine with the iron and loosen it from the fabric, then hold it in suspension in the water. However, these are often only designed for use on white or colourfast fabrics Be very careful, also, as these acids are highly poisonous.

I'd definitely recommend a product called Magica. It works well to get rust stains out of clothing as well as rust stains on a variety of other materials. It's available from The Rust Store. http://www.theruststore.com/Magica-Rust-Remover-Gel-P62C0.aspx

white vinegar or lemon juice