I would buy a laundry rust treatment chemical.
Hi Sheila, you can try this tip. https://www.hometalk.com/607726/how-to-remove-a-rust-stain-from-fabric
Sheila....I would try Blue Magic from AutoZone. It works on soooo many fabric and carpet
Hi Sheila: You can combine equal amounts of salt and lemon juice, and stir to make a thickish paste. Then (gently!) rub this onto the stain. White vinegar. Just like lemon juice, white vinegar is a natural anti-rust remedy. Here's a site that may help: https://www.omo.com/au/laundry/laundry-tips/stains/how-to-remove-rust-from-clothes-even-your-whites.html Good luck