AbstractCorrosion of steel in reinforced and prestressed concrete structures exposed to the marine tidal zone is a severe durability problem. This study used several indices related to moisture and chloride penetration into concrete to assess corrosion initiation severity in the tidal zone. A chloride transport model for simulating chloride penetration into concrete exposed to tidal wetting and drying is developed in the present study. The model was validated with published experimental results from three different studies. The simulated moisture and chloride profiles in the tidal zone were characterized using moisture and chloride penetration indices identified from the existing literature. Correlation between the moisture and chloride penetration indices was explored. A comparison was drawn between the penetration indices evaluated using two different tide models: (1) the conventionally used diurnal tide model, and (2) a more realistic superimposed tide model. A comprehensive sensitivity analysis was carried out to understand the influence of various model parameters on the penetration indices. Results of the study revealed a reasonable correlation between the chloride concentration peak–related indices and the moisture penetration indices in concrete. However, the chloride threshold depth–related indices did not correlate well with the moisture penetration indices. The proposed superimposed tide model gave more realistic and conservative predictions of the penetration indices than the conventionally used diurnal tide model. The models and data presented in this study facilitate a more realistic prediction of corrosion initiation time in the tidal zone.