The corrosion prevention mechanism and edge corrosion of the galvanized steels have been investigated. The atmospheric exposure tests were carried out for the observation of corrosion process on the specimen surface under the seashore environment for one and half years. The wet and dry corrosion cycle tests controlled at 33%RH and 84%RH after dropping 0.5M NaCl solution were carried out for the investigation of corrosion morphology on the galvanized steel. From the results of the exposure tests and the wet/dry cycle tests, it was indicated that the galvanized steel was protected by the corrosion product of Zn under the atmospheric environment. The anodic polarization curve measurements were carried out for the exploration of the anodic polarization behavior under the neutral solution. According to the results in the anodic polarization curves of the galvanized steels, the anodic current density of the edge part was larger than that of the surface part.