Dissolving 304 Stainless Steel We installed 20 2" drop in anchors to anchor several signs in place near the entrance of our pool. We have to remove the signs about twice a year and after the end of the past season, I noticed there is a small amount of rust forming. I purchased the 304 because it was not going to be in direct contact with the water and because it was solid, not coated, as opposed to the 314, which was only coated. It seems as though the 304 was also just coated so it is beginning to rust. I need to provide some sort of plan as to how to remove the 304 anchors and replace with 316.

Drop in anchors are not made to come out of concrete as the driving pin expands the bottom into place. I had thought about drilling them out but I am hoping to use that as a last resort because I don't want to damage our new concrete and need to keep the holes in tact. I read that Nitric acid can dissolve stainless steel. Will this work in my situation? Or will that also damage the concrete?
You are not going to dissolve 304 and leave the concrete. Use sandpaper to remove the surface rust as needed : Or mechanically ( cut/grind) the 304 to remove it.