Sometimes, the stain is just too old or too deep. That’s when you need to bring in the big guns. Look for a product labeled specifically for “rust stain removal” – brands like Whink or Zout make good ones. These usually contain hydrofluoric acid or oxalic acid, which are very effective but also strong chemicals.
What To Use To Remove Rust From Clothes at Gregory Ware blog
Follow the instructions to the letter. Wear gloves. Work in a well-ventilated area. I once ignored the “test on a hidden area” part, and my favorite jeans developed a lighter spot that looked like a weird birthmark. Learn from my mistakes, folks. Test first.