Mauviel Carbon Steel fry pan has rusted. How do you remove the rust?
Fine steel wool will work.
So will a bath of 50% distilled vinegar and water.
Steel wool will do the best job, but either way you are going to have to re-season the pan otherwise you will get strong metallic flavors.
If it's just a small area you can scrub it off with a nylon scratch pad (those green scrubby things). You can sprinkle a bit of salt too, to help with the scrubbing. You may not even need to re-season.
If it's a much larger area, I agree with the vinegar bath idea below. And yes you would need to season in this case.
Thanks to all who responded. They weren't that rusted and a little bit of steel wool cleaned them up nicely.