The effect of galvanized corrosion steel sheets and zinc-rich primer coated steel sheets on the perforation corrosion of actual automobiles and the relevant corrosion mechanism was studied. Perforation occurred in 6-7 years for zinc-rich primer coated steel panels inside of door hems and after more than 14 years for galvanized steel sheets with 120g/m2 zinc coating mass in the lapped side-sill. Perforation corrosion of galvanized steel panels can be divided into 4 corrosion processes on the basis of measured perforation depth and analysis of iron rust for North American automobile bodies. The period in which zinc corrosion controls the corrosion of the steel substrate played a very important role in determining the period until perforation occurs in road salting regions.