A study of "inside-out" auto body corrosion was performed by examining rust layers on five junked and three operational cars which exhibited quarter panel corrosion perforations. Model years included 1969 to 1974, and mileages ranged from 49,000 to 114,000. The three major American manufacturers were represented. Some perforations had occurred within three years of service life, and it is noteworthy that such corrosion rates [10 to 15 mpy (254 to 381 μm/year)] are similar to those for the very aggressive splash zone condition in seawater corrosion.
Specimens up to 2 ft2 (1858 cm2) in size were obtained by hand shearing from areas adjacent to perforations. Some losses of loosely adherent rust layers were unavoidable in this operation. Metallographic specimens were prepared by carefully hand shearing relatively large areas from the field samples and vacuum mounting them in cold setting epoxy. Conventional saw cutting of smaller specimens...
