This work is a preliminary examination of mechanistic issues on the comparative corrosion
performance of regular epoxy-coated rebar (ECR) and dual polymer-zinc coated reinforcement (DCR) in
simulated concrete pore solution with and without chloride ions, at polarizations from +100 mV to -1000
mV in the saturated calomel electrode (SCE) scale and exposure periods of 1 month or longer. Both
materials had intentional coating breaks exposing the base steel. Polymer adhesion degradation of DCR
relative to the as-received condition was comparable to, or less than, that experienced by ECR under
both anodic and cathodic polarization and with and without chloride ions. Both DCR and ECR
experienced severe corrosion at breaks under strong anodic polarization with chloride ions, but distress
for DCR was significantly less than for ECR. Under open circuit conditions DCR experienced an initial
high activity period both in the presence and absence of chloride ions after which the open circuit
potential stabilized to ~-400 mVSCE, and the exposed steel remained free of corrosion in either
environment. In contrast, ECR in the presence of chlorides developed more negative open circuit
potential (OCP) and visible corrosion. After the initial period of high activity, OCP consumption of the
zinc exposed at the defect rim proceeded at a very low rate both in the presence or absence of chloride
ions. In the absence of chloride ions and under medium to strong cathodic polarization, DCR showed
cathodic current (and hence an ability to support corrosion macrocells with through-the-steel defects) no
greater than that for ECR.
Keywords: epoxy, zinc, dual-coat, disbondment, rebar, corrosion