How do I remove rust stains from from metal buttons on a white cotton canvas ski coat?

They make a product to remove rust stains. I was in the caribbean and put my white bathing suit cover up on a rusty hanger and came home with it covered with rust stains. I cannot remember the name of the product but I know I purchased it at Jo-ann Fabrics and it was specifically used to remove rust. I just added it to the wash water and it removed all of the rust stains without having to do it twice! It was specifically made to remove the rust. Just ask the staff at the local Joann's. They can probably help you find the product. The company makes all different sorts of formulations to get all different kinds of stains out! Great product...if I could only remember the name.  more