In marine environments, structures are subjected to a variety of environmental conditions which govern the degradation processes. For reinforced concrete structures these degradation processes (chloride ingress and corrosion) are driven by the availability of oxygen and humidity. Due to the random process of tidal movements, it is difficult to determine the spatial boundaries of the major exposure zones related to reinforcement corrosion, namely, tidal, splash and atmospheric. In this paper a method is proposed to assess these zones from the interpretation of corrosion potential and resistivity data obtained from on site measurements dedicated to reinforced concrete structures in marine environment. A database has been established using measurement results from several piers of the "île de Ré" bridge in France. The robustness of the method was studied considering various climatic conditions representative of the seasons in the West Atlantic coast of Europe.