# Review of Structural Health Monitoring Techniques in Pipeline and Wind Turbine Industries
## 3 Health Monitoring in Corrosion
### Distributed OFS for Chemical Sensing
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**SI No** & **Name of SHM** & **Nature of Technique** & **Applicable** & **Precision of Damage** & **Use for** & **Potential to Predict** \\  & **Technique** & **Infrastructure** & **Detection** & **Oil-Based Conduit** & **Future Damages** \\ \hline \multirow{3}{*}{1} & Corrosion & Coupon is placed within the & Can be applicable for & No precision position & Can work for & Difficult to predict \\  & Coupon & working material and is thus & pipe/reactor of any & and time of & water-based system & any future damage \\  & & invasive & shape or size & & leak/corrosion & & location \\ \hline \multirow{3}{*}{2} & Electrical & Invasive probe works as a & Can be applicable for & No precise positioning & Real-time data may & be utilized to detect \\  & Resistance Probe & real-time corrosion coupon & pipe/reactor of any & but time and extent of & Can work for oil or & the future damage \\  & & shape or size & & corrosion or mass loss & water-based system & or probable future \\  & & & shape or size & can be determined & & leaks \\ \hline \multirow{3}{*}{3} & Electrochemical & In-situ electrochemical & Can be applicable for & No precise positioning & Work better for & \\  & Sensors & corrosion rate determination & pipe/reactor of any & but time and extent of & Electrally imposed & Any future damage \\  & & shape or size & & corrosion can be & potential may & location \\  & & & shape or size & determined & increase & \\  & & & & electronchemical & & \\  & & & corrosion rate & & \\ \hline \multirow{3}{*}{4} & Ultrasonic & Ultrasonic probes are placed & & Precision is better than & & \\  & (Acoustic) Testing & inside the pipe to detect pipe & Can be applicable for & Real-time positioning is & Real-time data may & be utilized to detect \\  & Sensor & thickness, flow change, or & pipe/reactor of any & possible. However, very & water-based system & the future damage \\  & & loss & & shape or size & small leak or structural & or probable location \\  & & & damages are difficult to & determine using this & & of leaks in future \\  & & & technique & & & \\ \hline \multirow{3}{*}{5} & Magnetic Flux & Invasive technique for & Can be applicable for & Can be applicable for & Can not precisely locate & Can work for oil or & Using this \\  & Leakage Method & detection of damage in & pipe of any shape or & the position of structural & Can work for oil or & become difficult to \\  & & magnetic flux lines & size & damage & & predict any future \\ \hline \multirow{3}{*}{6} & Point OFS for & Works as an optical corrosion & & No precise positioning & Can work for oil or & Difficult to predict \\  & & coupon using optical & cupron from its position & pipe of any shape or & but incidence and extent & water-based system & any future damage \\ \cline{1-1}  & Corrosion & inside the pipe & size & determined & structural damage & location \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Techniques of SHM and their descriptions. Figure 12: Metallic thin film-coated optical fiber sensors (OFS) for distributed corrosion sensing interrogated using Optical Frequency-Domain Reflectometry (OFDR) [71]: (**a**) Rayleigh backscattered light increases as the corrosion of Fe proceeds due to light absorption of metallic film; (**b**) Microstrain on the fiber increases with mass loss of coated Ni film due to release of compressive internal stress induced by Ni deposition. Note: (1)—single-mode fiber core; (2)—cladding; (3)—polymer jacket; (4)—coated metallic film; (5)—multi-mode fiber core. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**SI No** & \begin{tabular}{c} **Name of SHM** \\ **Technique** \\ \end{tabular}  & **Nature of Technique** & **Applicable** & **Precision of Damage** & **Use for** & **Potential to Predict** \\  & **Technique** & **Nature of Technique** & **Infrastructure** & **Detection** & **Oil-Based Conduit** & **Future Damages** \\ \hline \multirow{8}{*}{7} & \multirow{8}{*}{ \begin{tabular}{c} Quasi- \\ Distributed OFS \\ for Corrosion \\ \end{tabular}