i have found trying baking soda made into a paste and a scrub brush. if that doesnt work CLR takes most rust stains out.
CLR (Calcium, Lime Rust) Remover.
Try CLR or an OXY cleaner.
Try some CLR, calcium lime rust remover
CLR its found at most harware stores. scouring stone
Try CLR. It removes rust from many things without damage.
Bleach will help with the smell. Rust removal products such as CLR can remove the stains. But, never mix the two.
You may need to replace it but you can remove it and try CLR and then rinse it really well.
There are a number of products commercially available in hardware stores and in the cleaning product section of supermarkets. One such product is CLR which advertises for removing Calcium or Lime deposits, or Rust stains.
CLR is a household cleaner used for removing Calcium, Lime, and Rust. It's commonly used for Kitchens and bathrooms.
Use limeaway (the concentrated type) or clr (concentrated). Both work pretty well. They are very strong and can be bought at home depot or lowes.
If it starts to rust then it most definately will leave a rust mark on the concrete.