Corrosion behavior of epoxy-coated reinforced bars in RC test specimens subjected to pre-exposure loading and wetting-drying cycles

• Performing five-time electrochemical measurements of the bars.
• Reporting variations of electrochemical data with time.
• Observing microstructure of coated-bar samples via SEM and EDS.
• High stress in bars and wide concrete cracks result in reduced coating adhesion of coated-bars.
• Proposing corrosion resistance deterioration mechanism of in-service RC elements with coated-bars.

In the present paper, five-time electrochemical impedance spectroscopy (EIS) data of uncoated and epoxy coated-bars in RC test specimens subjected to pre-exposure loading and three wetting-drying cycles are reported. Variation of electrochemical data of the reinforcing bars with cycle time is shown basing on the test results. On the basis of electrical equivalent circuits fitting results, variation of coating resistance of the coated-bars with cycle time is presented. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) results of the cross section of the samples used are also presented. The influence of pre-exposure loading on the corrosion behavior of reinforcing bars in RC test specimens is mainly discussed on the basis of pre-exposure loading results, EIS fitting results as well as SEM and EDS results. Based on this discussion, a deterioration mechanism of corrosion resistance of epoxy-coated bars in RC elements subjected to in-service loads and environmental attacks simultaneously, is proposed. It is concluded that coating adhesion and corrosion resistances of epoxy coated-bars are greatly influenced by pre-exposure loads and simulated seawater solution attacks, especially in zones where coat-bars are highly stressed and load-induced cracks in concrete cover are wide.