The zinc-coated sheets are widely used in auto industries, especially for body parts. Corrosion caused to the body parts by sea salts and deicing salts such as NaCl, MgCl2 and CaCl2 has raised concerns of the automakers. The role of Mg and Ca cations in is still intriguing [1], and the corrosion products formed under such condition could rather prolong the service life of galvanized steels. In this study, by combining the non-destructive electrochemical impedance spectroscopy (EIS) method and morphology observation, the benefit of alkaline metal cations on enhancing the corrosion resistance of galvanized steels has been investigated through accelerated lab test. A commercial hot-dip galvanized steel having the coating thickness of 10 μm was employed as the specimen. The amounts of chloride salts deposited on the specimen surface were 4.05 g/m2 for MgCl2, 4.75 g/m2 for CaCl2, and 5.00 g/m2 for NaCl so that the chloride amounts were fixed to be 3.05 g/m2. The salt coated specimens were exposed to the dry-wet cycling over 95 % RH (2 h) - 40 % RH (2 h) in the humidity chamber. EIS and polarization curves were measured at the certain intervals of the exposure to evaluate the stage of degradation of the coating. The corrosion products were examined by X-Ray diffraction (XRD) and scanning electron microscope with an energy dispersive X-ray detector (SEM-EDX). The specimens deposited with MgCl2 exhibited far better corrosion resistance than those with NaCl. Even after 15 weeks (630 cycles), the open circuit potential held at around -0.9 V (vs. SSE), indicating the remain of metallic zinc coating. The corrosion rate estimated by EIS results was also low. This high corrosion resistance was ascribed to a thin and homogenous corrosion product layer, which was mainly composed of Zincite (ZnO) and Simonkolleite (Zn5(OH)8Cl2·H2O). After 126 cycles of the exposure, the corrosion products were turned to a double-layer structure of which the inner layer was dense and outer layer was porous. The compact inner layer must have offered the high corrosion resistance under the extended term of the aggressive environment. However, such a structure and long state of protection was not observed under NaCl salt films [2]. Alkaline metal chlorides are less aggressive to corrosion of the galvanized steel than NaCl and could promote the formation of homogenous corrosion product layer. Reference [1] Yumiko Tsurumaki, Eiji Tada, Azusa Ooi and Atsushi Nishikata, Anodic Polarization Behavior of Zn in Aqueous MgCl2 Solutions, 2018, ECS Meeting s, No. 1056 [2] Y. Liu, A. Ooi, E. Tada, A. Nishikata. Electrochemical Monitoring of Degradation Process of Galvanized Steels in Atmospheric Environments, 2018, ECS Meeting s, No. 1058 Figure 1