## 2 Background: The INESSCOM Monitoring System  
Before the experimental plan is presented, the INESSCOM system and the protocol established for measuring and monitoring embedded rebar corrosion need to be presented. This tool has been presented and validated in previous works [41; 44; 45; 46], but the authors have continued to work on improving it [41]. The system comprises a network of sensors placed in different zones of a given structure which are defined as control points (CPs), as depicted in Figure 1. At each CP, a corrosion sensor is embedded, which is made of metal with identical properties to those of the structure's rebars, whose surface that comes into contact with concrete is known. In the insertion zone, there must be an electric connection with the closest rebar. The wiring of the sensor and rebar is led to a central module where microprocessors are placed. In electrical terms, the sensor has four positions. In the first one (Position 1), the sensor and rebar remain electrically connected, which allows the sensor to electrically participate in the macrocell processes that occur in RCSs while no measurements are taken. This is fundamental for the sensor to remain under the same conditions as the closest rebars [47]. When measurements are taken, microprocessors distinguish three positions; the first measurement to be taken is the macrocell current analysis (Position 2). In this case, it is an amperometric measurement taken to determine (\(i_{CORR,MACRO}\)). In the measurement protocol, taking the value 3 min after measurement commences is considered to allow the measurement to stabilise. Second (Position 3), the INESSCOM system employs a novel measurement system to determine the sensor's corrosion intensity (\(i_{CORR,MICRO}\)). This technique, defined as PSV (Potential Step Voltammetry), has been previously validated [48; 49; 50] and is based on reconstructing the straight stretches of the anodic and cathodic Tafel extrapolation curves. This representation is obtained from analysing the intensity-time response (\(I\) vs. \(t\)) as opposed to potentiostatic-type disturbance (\(\Delta E\)). Moreover, its instrumentation does not require having to employ reference electrodes because the technique has been developed to be used in a two-electrode cell, where the sensor acts as the working electrode and the rebar as the pseudoreference electrode. This avoids having to resort to using reference electrodes, whose long-term reliability and stability in a measuring cell where traditional electrochemical techniques are employed have not yet been proven [51]. Furthermore, signal processing can be automated, which does away with the need to rely on humans supervising the whole process [41]. To know the sensor's total corrosion intensity, it is necessary to bear in mind both the macrocell current and the sensor's corrosion, \(i_{CORR}=i_{CORR,MACRO}+i_{CORR,MICRO}\), as previous works have demonstrated [41; 47] and as several authors have pointed out [3; 52; 53; 54]. When corrosion measurements end, the INESSCOM system determines the sensors' double layer capacity (\(C_{DL}\)) by Cyclic Sweep Voltammetry (CSV), as other authors in the corrosion field have used [55; 56; 57], and as validated in a previous work [33]. When this last measurement has been taken, microprocessors return the sensor to Position 1 until the next measurement is taken.  
When measurement ends, and thanks to the designed microprocessors, the system is capable of collecting data and transferring them to a central control so they can be viewed [44]. In this way, an autonomous protocol is generated in which the system performs the corrosion assessment and corrosion monitoring to offer a final result. This  
Figure 1: The INESSCOM monitoring system.  
makes INESSCOM an extremely useful tool for the structural health monitoring and management sector that focuses on remotely assessing corrosion in RCSs.