Impedance Characteristics of the Carbon Steel under Cathodic Potential and Determination of an Optimum Protection Potential

It was theoretically shown in a previous paper (1) that ac impedance technique can be successfully utilized for determining and monitoring the optimum cathodic protection potential of the metals in a neutral solution. In this paper, the experimental studies have been made in order to support the theoretical analysis. The potential dependence of the faradaic impedance of carbon steels in 3.5% NaCl solution has been measured by ac impedance technique. The faradaic impedance showed a maximum at -0.70V with respect to sat. Ag/AgCl electrode. The cathodic protection efficiency obtained from weight loss also showed a maximum at the same potential, Therefore, the potential of faradaic impedance maximum corresponds well to the optimum cathodic protection potential, as the theoretical analysis has shown. It was concluded that the ac impedance technique is a promising method for determing as well as monitoring the optimum cathodic protection potential.