*2.4. Electrochemical Test*

Over the nine-year period, the steel's behavior was monitored using the electrochemical impedance spectroscopy (EIS) technique to determine the characteristics of the concrete–steel interface. The study configuration is shown in Figure 2. The characterization was performed with a Gamry Interface 1010 ETM potentiostat/galvanostat. A 10-mV sinusoidal signal was applied in one sweep at frequencies ranging from 10<sup>5</sup> Hz to 10−<sup>3</sup> Hz. The modeling of the equivalent electrochemical circuits was carried out with the Echem Analyst software.
