Corrosion processes and field performance of epoxy-coated reinforcing steel in marine substructures

Severe corrosion of epoxy coated rebar in the substructure of marine bridges in the Florida Keys has prompted an investigation of the condition of other bridges in the State. Over thirty bridges were subject to field examination, which included determination of rebar condition, determination of extent of electric continuity between rebars, extraction of concrete cores, determination of chloride diffusivity, concrete resistivity measurements, and related electrochemical measurements. The results indicate that the time for development of external corrosion symptoms in the Florida Keys was dominated by the corrosion propagation stage, which in that case was comparable to that expected for plain rebar. Structures outside the Florida Keys were found to be generally corrosion-free. Extensive metal-coating disbandment was observed in virtually all structures whether or not significant chloride contamination existed at the rebar level. Chloride penetration was very slow in bridges with modem concrete formulations, suggesting that long corrosion-free service times are likely for those structures. It is expected that the corrosion-free service life in those structures will be primarily the result of concrete quality and thick cover, and not necessarily due to the use of epoxy-coated rebar.