i sandblasted my whole truck(UGHH!) but i did it little by little, and i used the phosphoric acid on it...don't wash it off, the acid is water soluable, then you will have bare wet steel ripe for rust.my truck is under a carport and during some of our florida thunderstorms i found out that the windblown rain had some spotty surface rust coming back. now i hung plastic sheeting on the carport and treated the surface rust again with acid.good stuff. Before i sprayed the primer, i took some fine sandpaper and green scrubpads to get the powder residue from the ospho off.I know some guys will say that's alot of extra work, but i have limited resources and time to work on my truck...i just keep chippin away at 'er! thumbs_up http://s48.photobucket.com/albums/f216/applebag/?action=view&current=Markspics013.jpg