Working on a old Dodge W-300. The gas tanks had some bad gas and rust inside. Got rid of the gas and now am cleaning them out. Hot tanks are not legal any more where I live so I'm on my own. Got rid of most of the rust by putting some B-B's inside and driving around with the tanks in the bed of my truck. Then used air to blow out the dirt. Now I want to use some chemical to clean the rest of the rust out before I coat the insides. Any body know what I can use to get rid of the rust?