Corrosion Performance of Epoxy-coated Rebar in Florida Keys Bridges

Severe corrosion of epoxy coated rebar in the substructure of 5 major marine bridges in the Florida Keys was detected after only a few years of construction. Corrosion occurred underneath the coating and was preceded by loss of adherence between the steel and the coating. Damage surveys of the bridges, which were built around 1980, were conducted from 1986 to 2000. Corrosion resulted in delaminated areas (spalls) typically about 0.3 m each. After Initial detection, damage has been steadily accumulating at a rate of approximately 0.1 spall per bridge pier (bent) per year. An initiation-propagation model for corrosion development reproduced the observed trends. The exploratory model assumes distribution of chloride diffusivity, rebar cover, chloride surface concentration, and propagation time. Interpretation of the results suggests that much of the early damage stemmed from rebar with high levels of coating distress, and that damage development depends mainly on the propagation stage of corrosion.