There are a few different ways to remove rust from knives.
One way is to use white vinegar. Soak the knife in white vinegar for a few hours, then scrub with a stiff brush. Rinse with water and dry thoroughly.
Another way is to use lemon juice. Soak the knife in lemon juice for a few hours, then scrub with a stiff brush. Rinse with water and dry thoroughly.
You can also try using baking soda. Make a baking soda paste and water, and rub it into the rust stains. Let it sit for an hour, then scrub with a stiff brush and rinse well.