The corrosion behaviors of the isolated short and vertical long scale Q235B steel in a simulated tidal zone were studied by electrochemical impedance spectroscopy （EIS） monitoring and corrosion weight loss calculation in an experimental indoor simulating trough. The results show that the corrosion rate of the isolated short scale Q235B steel in the tidal zone acquired by the EIS agrees with the corrosion weight loss result. The corrosion rates of the short scale steel are in the order of middle tidal zone 〉 the central zone between the middle tidal zone and low tidal zone 〉 high tidal zone 〉 low tidal zone. The fastest corrosion rate in the middle tidal zone is attributed to the longest wet time in a tidal cycle. According to the comparison of corrosion weight loss between the vertical long scale and isolated short scale specimens, the corrosion rate of vertical long scale specimens of Q235B steel is lower than that of the isolated short scale specimens in the tidal zone, but the result is contrary in the immersion zone.
