## 3 Results
### Sem  
To study the corrosion behavior of the API 5L X65 samples after potentiodynamic polarization, the SEM technique was used to analyze samples A1 to C3. Table 7 shows the SEM images of the sample surfaces along with their EDX data for samples at 0 m/s (A1, A2, A3), 1 m/s (B1, B2, B3), and 2 m/s (C1, C2, C3). The first row of Table 7 gives the SEM image of the API 5L X65 samples before corrosion, completely polished without any corrosion. The EDX data show that the Fe concentration is the highest among all the other cases, depicting the least corrosion on the surface. It is a well-known fact that EDX results only show the elemental composition of the specimen surface and cannot indicate oxide layer formation, but the EDX data clearly show the oxygen elemental concentration increasing and iron elemental concentration decreasing, thus indirectly implying oxide layer formation on the surface of the specimen. The SEM images confirm this observation.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Number** & **3D View 50\(\times\)** & **3D View Distributed 50\(\times\)** & **Location 1 (100 \(\mu\)m)** \\ \hline C1 & & & \\ C2 & & & \\ C3 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Cont.  
For samples A1, A2, and A3 at 0 m/s flow velocity, the surface has started to become covered with corrosion product, which is formed by the reaction between the Fe, O\({}_{2}\), and OH- forming the ferric oxyhydroxide. This was revealed with the help of EDX data, which show the traces of the Fe concentration reducing and the oxygen concentration increasing along with the presence of chlorine as compared to fresh samples. For samples B1, B2, and B3 at 1 m/s flow velocity, the surface has less formation of loosely covered corrosion product as compared with A1, A2, and A3, which may have been removed by the velocity of the liquid in the system. However, we can observe the formation of small pits on the surface initiating localized corrosion over the metal surface. The EDX data for samples B1 to B3 show the formation of both ferric oxyhydroxide and ferric chloride, which is found in the pits generated at the surface. For samples C1, C2, and C3 at 2 m/s velocity, the material surface shows the formation of both the corrosion product and pits, but larger in size and greater in number as compared to samples at 1 m/s. The EDX data show that the chlorine concentration has increased as compared to samples at 1 m/s, which is because of the formation of more pits on the metal surface.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample Name** & 500 \(\mu\)m & 20 \(\mu\)m & **SEM EDX** \\ \hline \hline \end{tabular}
\begin{tabular}{c c c} \hline \hline Element & Wt \% & At \% \\ C K & 1.28 & 5.48 \\ O K & 1.57 & 5.05 \\ MnK & 1.86 & 1.74 \\ FeK & 95.29 & 87.73 \\ \hline \hline \end{tabular}
\end{table}
Table 7: SEM Images of API 5L X65 samples.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Name** & 500 \(\mu\)m & 20 \(\mu\)m & \multicolumn{2}{c}{**SEM EDX**} \\ \hline Element & Wt \% & At \% \\ C K & 1.69 & 5.64 \\ O K & 13.20 & 32.98 \\ NaK & 0.29 & 0.50 \\ ClK & 0.38 & 0.43 \\ MnK & 1.42 & 1.04 \\ FeK & 83.01 & 59.42 \\ \hline Element & Wt \% & At \% \\ C K & 3.73 & 14.51 \\ O K & 2.10 & 6.15 \\ NaK & 0.33 & 0.67 \\ ClK & 0.10 & 0.13 \\ MnK & 1.61 & 1.37 \\ FeK & 92.14 & 77.17 \\ \hline Element & Wt \% & At \% \\ C K & 2.95 & 11.59 \\ O K & 2.73 & 8.04 \\ NaK & 0.45 & 0.93 \\ ClK & 0.22 & 0.29 \\ MnK & 1.99 & 1.71 \\ FeK & 91.66 & 77.45 \\ \hline Element & Wt \% & At \% \\ C K & 2.90 & 9.99 \\ O K & 9.54 & 24.69 \\ NaK & 0.22 & 0.40 \\ ClK & 0.36 & 0.42 \\ MnK & 2.27 & 1.71 \\ FeK & 84.72 & 62.80 \\ \hline Element & Wt \% & At \% \\ C K & 2.21 & 8.59 \\ O K & 4.33 & 12.63 \\ NaK & 0.47 & 0.96 \\ ClK & 0.30 & 0.40 \\ MnK & 1.81 & 1.54 \\ FeK & 90.87 & 75.89 \\ \hline \hline \end{tabular}
\end{table}
Table 7: _Cont._