A full immersion test in simulated seawater was conducted to investigate the corrosion behavior of Zn-6%Al-3%Mg alloy-coated steel sheets (ZMA) and hot-dip galvanized steel sheets (GI). The study utilized weight loss analysis, electrochemical testing, SEM (Scanning Electron Microscopy), and XRD (X-ray Diffraction) analysis. The results showed that after 105 days of immersion in static seawater:The white rust coverage on GI samples exceeded 90%, while on ZMA samples it was less than 10%.The weight loss method revealed that the corrosion rate of GI was more than ten times that of ZMA. SEM observations indicated that the corrosion products on the ZMA surface were uniformly distributed and dense, whereas those on the GI surface appeared in clusters. XRD analysis revealed that the main corrosion product on the ZMA surface was Zn5(OH)8Cl2·H2O, while the primary corrosion product on the GI surface was ZnO. Electrochemical tests using simulated seawater as the electrolyte showed that the initial corrosion potentials of both materials were similar. However, the corrosion current of ZMA was slightly lower than that of GI. After corrosion, the corrosion potentials of both materials remained similar, but the corrosion current of GI increased compared to its original sample, whereas the corrosion current of ZMA decreased compared to its original sample.