Effect of Cyclic Potentiodynamic Passivation on the Passive and Electrochemical Behavior of a Mild Carbon Reinforcing Steel in an Alkaline Media Simulating the Concrete Pore Solution

In this work, the effect of cyclic potentiodynamic passivation (CPP) on the passive and electrochemical behavior of a mild carbon reinforcing steel in an alkaline media simulating the concrete pore (0.1 M NaOH.1 M KOH) solution was studied by electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis. Nyquist and Bode plots revealed that the passive film resistance of mild carbon reinforcing steel was increased by applying further CPP cycles. Mott–Schottky analysis showed that the passive films behave as both n-type and p-type semiconductors depending on the potential. Moreover, this analysis revealed that the semiconducting character of the passive films was not altered by CPP method. Also, it was found that both donor densities reduced by increasing the number of CPP cycles. More noble free potentials, smaller cyclic voltammogram loops, larger imperfect semicircles in the Nyquist plots, and less donor densities within the passive film were all indications of the positive effects of CPP. All electrochemical measurements revealed that the electrochemical behavior of mild carbon reinforcing steel was enhanced under the effect of CPP method, mainly attributed to the formation of thicker yet less defective passive films.