l have some galvnaized steel posts under my house with some minor surface rust, my plan is to apply a rust killer/ converter and then paint over them with rust quard paint, l was thinking of using Rannex rustbuster but you are not supposed to use it on galvnized steel because it damages the galvanized coating, can anyone tell me a brand or a name of a good rust killer/ converter that is good and safe to use on galvanized steel