If rusty metal buttons to dye clothes, how to deal with?

Buttons on cotton rust stains on clothes, and how to get clean?

I believe many people have trouble in this regard. Below me, a little way down.

Soiled clothes iron stains, the available 2% oxalic acid solution at about 50 ℃ removed by washing in warm water, then rinse with water. With 3 to 4 vitamin? After pills crushed into powder, sprinkle soaked clothes dirty, and then scrub with water several times, but also to remove rust stains. Chen case rust stains can be washed with 10% oxalic acid, citric acid plus water mixture will stick rust at the wet, and then immersed in the brine, 1 day wash. So afraid of buttons rusty, but the choice of good quality buttons, not prone to this situation.