The Ospho will turn the rust a darker sorta shinier look and help keep it from getting wore. I will leave a powder on it but wipe that off. I will look much better also. IF you prime it with an epoxy primer, always neutralize the Ospho to be safe. That is respray a heavy coat on let it sit a little and wash it off GOOD with water. Some brands of epoxy can react with the Ospoh ( phosphoric acid solution)...