Effect of Cathodic Protection on Epoxy-Coated Rebar

摘要

In anticipation of the future need to use cathodic protection (CP) on existingconcrete structures reinforced with epoxy-coated rebars (ECR), this study sought to determine if CP can effectively mitigate corrosion of ECR without adversely affecting the rebar/concrete interface and to examine the effect of CP on the disbonding characteristics of the coating/rebar interface in the concrete environment. Hybrid cell concrete samples, reinforced by ECR with international coating defects, were designed to allow for cathodic polarization, electrochemical interrogation, and mechanical testing of rebar pullout characteristics. Cathodic polarization was conducted at four current levels (0X, 1X, 5X, and 10X of 1.08 micrometersA/square centimeters, scaled to a 1% coating defective area) and three time intervals. Five replicate samples were used for each condition. Open-circuit potential measurements, electrochmical impedance spectroscopy, and linear polarization were performed on each sample priot to, during, and after the application of CP. After each CP exposure, the load-vs.-strain behavior of the rebar was quantified in an MTS load frame using LVDT for strain determination. All electrochemical tests indicated that the CP current levels and application times used were effective in preventing corrosion of embedded ECR. The tests also revealed that the CP levels and times had no effect on the splitting failure characteristics, at a 95% confidence level. However, EIS tests indicated that the coating was delaminating at the periphery of defects, which was verified by post mortem SEM analysis. Although the levels of delamination in this study did not affect mechanical performance, it is recommended that the use of a protective level that does not induce film delamination be explored.