## 7 Corrosion Control and Monitoring
A total of 30,000 corrosion image datasets were trained using AlexNet as the HCDR network, and a classifier model to recognize the position and location of the corrosion was developed with an overlap-scanning sliding window algorithm. The proposed CNN model could detect various types of superficial structural damage, such as delamination, voids, and spalling and corrosion damage. In 2020, a comparison of the monitoring of long-term corrosion of carbon and stainless steel reinforcements exposed to the actual marine environment was intensely studied by [PERSON] et al. [131]. In the monitoring strategy, electrical resistance (ER) probes and coupled multi-electrodes (CMEs) were placed at five different exposure zones of these concrete columns for 52 months. The ER probes and CMEs were virtually connected through zero resistance ammeters (ZRAs). The ZRAs were then connected to a 16-bit analog-to-digital (A/D) converter. The observations showed that ER probes are able to detect corrosion initiation and propagation and detect localized corrosion. At the same time, CMEs can measure the spatio-temporal evolution of the corrosion process (microcell corrosion). The landmark research on sensor technology application for monitoring corrosion in the marine environment over the last decade is summarized in Table 10. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Authors** & **Observational Platforms** & **Tools/Instruments** & **Important Remark** \\ \hline [PERSON] et al. (2010) & Quasi-circular zone chemical corrosion on the submerged aluminum plate & Lamb-wave-based identification (pulse-echo measurement scheme) with the assistance of probability-based diagnostic imaging technique & Rectification and compensation are required for medium coupling when applying Lamb wave-based corrosion monitoring with coupled media. \\ \hline [PERSON] et al. (2013) & Steel rebar of coastal concrete & Anode–ladder system and Corrowatch System & Monitoring test corrosion state developed based on electrochemical polarization dynamics. The ohm-drop effect can be ignored to obtain a more accurate result. \\ \hline [PERSON] et al. (2014) & Steel structures (Q235B) in the marine tidal zone & Electrochemical impedance spectroscopy (EIS) & Simulating the marine tidal corrosion under laboratory test is feasible, and the comb-shaped double electrode probe is suitable for in situ EIS monitoring. \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Landmark research on the sensor technology applications for monitoring corrosion in various marine structures. Recently, [PERSON] et al. [132] conducted a benchmark autonomous detection and monitoring study of offshore wind turbines using real-time remote sensing technology. Under a project funded by Innovate UK, they invented smart wireless miniaturized sensors utilizing the Internet of Things (IoT) and integrated with satellite and terrestrial communication networks, named the iWindCr project. The arrangement plans of the iWindCr WSN system and the user interface prototype of iWindCr software are comprehensively illustrated in Figures 25 and 26, respectively. To detect and monitor the progress of corro