On my 05 envoy I have painted rust spots a number of times with expensive can paint and cheap can paint. Each time the result was the same about two days latter the rust showed through the paint. I have Sand blasted it down to clear metal (or so I thought) primed it and painted with three coats let them dry between coats but always the rust comes back.I have painted years before and never had this problem but I am far from being a pro. Is there an acid wash to use and if so what is the best. I think I have to neutralize the rust first but as I said I have never had to in the past. Thanks for the help. Tux05