Best rust killer/converter for galvanized steel post

Hi the galvanized Steel posts under my house have a bit of surface rust, l had a building inspector look at it and he said its nothing serious and wouldnt become a problem for many years but l thought l would take care of it soon, paying someone to do it would be expensive as its very time consuming so l thought l would do it myself, my plan is to apply a rust killer/converter before l paint over them with rust guard paint. l was thinking about using Ranex Rustbuster as l heard its very good but l read you are not suposed to use it on galvanized steel so l dont want to use that. My question is what is the best rust converter/killer to use on galvanized steel.