Will EDTA in aqueous solution remove superficial rust stains from concrete?

Answer 1

It wouldn't be a great way to do it, IMO. I would be afraid it would chelate the Calcium in the concrete, using up most of the EDTA before it goes after the rust stains. Try a hot solution of Oxalic acid and a little vinegar. It will still attack the concrete, but will oxidize the Fe into a soluble form.