Llimestone stains Paul 08 Sep 2010 16:54 EDT

There is a railing that when gets wet drips and stains my clients limestone deck. I've tried sanding the stains with 120 resin diamond pads. The grit actually matches the finish of the deck. While much if it has come out there is still some remaining. Was wondering if there was any quick effective methods anyone has found to remove these types of stains in the same day.