## 4 Conclusions  
The study of the corrosion behavior of carbon steel weldments in carbonated pore solution by using the coupled multi-channel electrode shows the following results:  
Figure 9: Schematic Evan’s Diagram illustrating the \(I_{corr}\), \(I_{Macro}\), \(I_{corr0}\), and \(I_{c}\). 1. A complete welded structure can be well simulated by using the coupled multi-electrode array sensor system. The OCP of the electrodes, the coupled potential, and the galvanic currents among the electrodes can be online monitored. The maximum penetration rate of the weldment can be measured when serious localized corrosion happens. The metastable pitting corrosion and stable pitting corrosion process can also be revealed by the sensor system. This sensor system can be used as an effective method to monitor corrosion of weldments in marine concrete structures. 2. The passive film on the WM area and the HAZ closings to the WM area are fragile and it is easier for them to be destroyed by the aggressive ions in the marine environment. These areas will confront high preferential corrosion risks and they always act as anodes when coupled with the BM area. Once stable pits were formed on the WM area or the HAZ, a localized anodic area will form and leads to a high penetration rate. The high galvanic current among the WM zone, HAZ, and BM zone will also result in the acceleration of the localized corrosion. The highest localized corrosion rate of the weldment in the carbonated pore solution containing 0.2 mol/L Cl\({}^{-}\) can reach a value higher than 0.8 mm/a, which will result in the fast failure of the marine structure. 3. The inhibitor NaNO\({}_{2}\) has an obvious inhibition effect on the corrosion of weldments when the ratio of NO\({}_{2}\)\({}^{-}\) and Cl\({}^{-}\) is 0.5. The maximum anodic current has a nearly 80 times decrease after the inhibitor was added. The OCP of the localized corrosion area also recovered with the introduction of the inhibitor. It indicates that NO\({}_{2}\)\({}^{-}\) has a strong repair function for the broken passive film on the WM zone and HAZ in carbonated pore solution. 4. The localized corrosion rate and the corrosion depths of the electrodes will be underestimated only based on the anodic current and anodic electric charges obtained by the sensor system. The electrodes with cathodic currents cannot be directly considered as the pure cathodic area. Both negative galvanic current and microcurrent may exist on these electrodes. For the pure anodic electrode, the main measurement error of the maximum localized corrosion rate is caused by its internal micro-current. When the coupled potential is close to the OCP of the pure anodic electrode, the measurement of the corrosion current at the OCP can provide a further evaluation of the maximum penetration rate. The following are available online at [[https://www.mdpi.com/article/10.3390/app11188278/s1](https://www.mdpi.com/article/10.3390/app11188278/s1)]([https://www.mdpi.com/article/10.3390/app11188278/s1](https://www.mdpi.com/article/10.3390/app11188278/s1)), Figure S1: Time dependence of the galvanic currents among the repeat sample#1 (a), the galvanic currents at 0 h to 28 h (b), the galvanic currents at 38 h to 61 h (c), and the galvanic currents at 61 h to 108 h (d), Figure S2: Time dependence of the galvanic currents among the repeat sample#2 (a), the galvanic currents at 0 h to 25 h (b), the galvanic currents at 36 h to 61 h (c), and the galvanic currents at 61 h to 108 h (d). [PERSON] and Z.M. : formulation, writing, and analysis of the paper. Y.Z. and X.W. : Data curation. Y.H., K.W., S.S. and W.J. : Supervision and Validation. All authors: data analysis, discussion, writing and revision of the manuscript. All authors have read and agreed to the published version of the manuscript. This research was supported by the Key-Area Research and Development Program of Guangdong Province (No. 2019B111105002). Not applicable. We thank [PERSON] for their technical support in the design of the experimental method. We declare no conflict of interest.