RE: ospho vs. eastwood rust dissolver
The best product I've found is Metal-Ready. It is a phosphoric acid and zinc phosphate solution and is a very good base for POR-15. It is a very good welding conductive product and is made by the same company as POR-15. All you need to do is clean any grease or oil off the metal, remove any paint scale or loose rust, spray the metal until very wet and keep it wet for at least 30 minutes.