Corrosion of reinforced concrete (RC) structures has been one of the major causes of structural failure. and the local potential do not change; differences were found only in the magnitude of potential gradients. In a structure with a high chloride concentration, there is usually low resistivity in the concrete. The readings are often mismatched when there is low resistivity in the concrete, but it has readings with high passive potential. This is due the fact that chlorides are transported more easily in lower resistivity of concrete, high contents of chlorides depassivated the steel reinforcement, and active potentials were measured [7]. Table 1 SAT1 Interpretation of corrosion activity of electrochemical methods. On the other hand, the polarization resistance method is commonly utilized for measuring the corrosion rate in RC structures. The method records the current generated and consumed by anodic and cathodic reactions. The change in potential during reactions is known as polarization, which is used to evaluate the steel corrosion. However, this electrochemical method has some limitations, such as the method assumes standard corrosion while pitting corrosion is usually a highly probable form of steel corrosion in buy 403811-55-2 concrete, which might lead to misleading results. In addition, the area of steel measured buy 403811-55-2 in concrete is not precisely known buy 403811-55-2 which creates some errors in the polarization resistance calculations. Another error in the polarization resistance method is the IR drop launched by high resistive medium and high separation of the reference electrode from your steel reinforcement of the RC structures [34,35,36]. Determine 1b shows the principal of polarization resistance method. The other practical method for measuring the corrosion rate is GPM. This generally entails impressing a small amplitude, short time anodic current pulse, to be applied galvanostatically around the steel reinforcement from your external counter electrode over the concrete surface [39,40]. The anodic current is usually in the range of 5 to 100 A and the typical pulse duration is usually between 5 and 30 s [19]. The steel reinforcement is usually anodically polarized and there is a resulting change in the electrochemical potential. The potential is recorded by a reference electrode (usually in the center of the counter electrode) as a function of polarization response. Determine 1c shows a schematic setup for the GPM test. When the constant current = V/I (2) where V is the standard deviation for the potential and I, the standard deviation for the current obtained by statistical analysis of the noise data. The main advantage of the EN technique is usually its lack of intrusiveness. It can avoid artificial disturbances to the system during measurement [57]. The EN measurement has been used to study the onset of localized corrosion [58,59]. However, only a few studies of EN for measuring corrosion in buy 403811-55-2 RC structures have been carried out [60,61]. Previous work using this technique on reinforcing bars has only analyzed the corrosion process of various metallic materials [62,63,64,65]. Table 1 provides a summary of the qualitative corrosion activity of the above electrochemical methods. However, there is no standardization for the evaluation of the corrosion activity by EN method. Therefore, most of the electrochemical methods require direct connection with the steel reinforcement in the RC structure as the electrode, which makes it an intrusive method [66]. It requires a localized breakdown in the concrete surface to provide the direct connection [67]. 2.3. Electromagnetic (EM) Waves Another NDT method of corrosion monitoring is usually ground penetrating radar (GPR), which is based on the propagation of an EM wave buy 403811-55-2 into an RC structure. Part of the EM wave is reflected back to the receiving antenna whenever it encounters an interface of two media with differing dielectric constants [68,69,70,71]. A GPR antenna receives direct and reflected waves, which are recorded as.