Galvanizing method is being widely used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and for some other fields etc.. However, galvanized structures inevitably may be corroded rapidly with increasing exposed time because the rate of environmental contamination is accelerating due to the rapid development of industrial society. Therefore, it is necessary to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment etc.. In this study, three types of the test specimens, that is, pure galvanizing, galvalume and chromate treated steels were immersed at inhibitor solution. And the effect of inhibitor for their corrosion resistance improvement was comparatively investigated with an electrochemical method. Corrosion current density of the original galvanizing and galvalume steel exhibited the highest and lowest value respectively in seawater. However, the corrosion resistance of these samples was considerably improved by dipped to a inhibitor solution(H3PO4+ Zn(NO3)2+Q). In particular, the galvanizing steel which dipped to the inhibitor solution exhibited the lowest corrosion current density due to the best effect of corrosion resistance improvement compared to other test specimens.