## 4 Discussion  
The potentiodynamic polarization data from Table 2 and the SEM images from Table 7 indicate that the corrosion rate and corrosion product formation vary from A1 to C3 of the API 5 L X65 samples for the various flow and magnetic conditions. These reactions occur due to the presence of various ions, such as H\({}^{+}\), OH\({}^{-}\), Fe\({}^{2+}\), and Fe\({}^{3+}\), formed in the solution. During the reaction of carbon steel in a near-neutral NaCl solution, the cathodic process may include the reduction of H\({}^{+}\) and OH\({}^{-}\) ions, which is shown in Equations (4) and (5), and the anodic reaction includes the dissolution of iron, as shown in Equations (6) and (7). Cathodic Reaction:  
\[\mathrm{O_{2}+2H_{2}O+4e^{-}}\rightarrow\mathrm{4 OH^{-}} \tag{4}\]  
\[\mathrm{2H^{+}+2e^{-}}\rightarrow\mathrm{H_{2}} \tag{5}\]  
Anodic Reaction:  
\[\mathrm{Fe}\rightarrow\mathrm{Fe}\;^{2+}+2e^{-} \tag{6}\]  
\[\mathrm{Fe}^{2+}\rightarrow\mathrm{Fe}\;^{3+}+e^{-} \tag{7}\]  
The presence of sodium chloride in the corrosion process complicates the corrosion mechanism depending upon the oxygenated and deoxygenated environment. Chloride ions accelerate the anodic reactions by forming intermediate corrosion species, and, due to the higher activity of H\({}^{+}\), the solution pH is decreased [39]. Fe\({}^{2+}\) ions then react with the OH\({}^{-}\) ions from the cathodic reaction in the presence of chloride ions to form the following corrosion product, as given in Equations (8), (9) and (10). \[\mathrm{Fe}^{2+}+2\mathrm{OH^{-}}\rightarrow\mathrm{Fe(OH)_{2}} \tag{8}\]  
\[\mathrm{4 Fe(OH)_{2}+O_{+}+2H_{2}}\rightarrow\mathrm{4 Fe(OH)_{3}} \tag{9}\]  
\[\mathrm{Fe(OH)_{3}}\rightarrow\mathrm{FeCOOH+H_{2}O} \tag{10}\]  
The hydroxyl (OH\({}^{-}\)) ions will be present in addition to the dissolved oxygen under high Cl\({}^{-}\) concentrations, leading to the formation of FeOOH, ferric oxyhydroxide [40]. On the metal surface, Cl\({}^{-}\) competes with the dissolved O\({}_{2}\) or OH\({}^{-}\), and Cl\({}^{-}\) favors the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Name** & \multicolumn{1}{c}{**500 \(\mu\)m**} & \multicolumn{2}{c}{**20 \(\mu\)m**} & \multicolumn{2}{c}{**SEM EDX**} \\ \hline  & & Element & Wt \% & At \% \\  & & C  K & 1.60 & 6.04 \\  & & O  K & 6.38 & 18.11 \\  & & NaK & 0.73 & 1.44 \\  & & ClK & 0.43 & 0.55 \\  & & MnK & 1.83 & 1.51 \\  & & FeK & 89.03 & 72.35 \\ \hline  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: _Cont._hydration of the metal ions and results in the increase in the metal ion migration from the metal surface to the bulk of the solution [41]. The most common ferric oxyhydroxoxide corrosion products are \(\alpha\)-FeOOH and \(\gamma\)-FeOOH in high salinity in oxygenated systems. For samples B1 to C3, small pits are observed on the surface after the potentiodynamic polarization, which is shown in Table 7. These pits are formed by the reaction of the Cl\({}^{-}\) ions with the Fe ions present in the solution, which is shown in Equations (11)-(15) [42; 43; 44]. The chloride ions present in the electrolyte solution aggressively attack the steel surface at the anodic region, which leads to the dissolution of the Fe ions continuously by uniform and pitting corrosion. \[\mathrm{Fe}+\mathrm{Cl}^{-} \rightarrow\mathrm{Fe}(\mathrm{Cl}^{-}) \tag{11}\] \[\mathrm{Fe}(\mathrm{OH})+\mathrm{Fe}(\mathrm{Cl}^{-}) \rightarrow\mathrm{Fe}+\mathrm{FeOH}^{+}+\mathrm{Cl}^{-}+2\mathrm{e}\] (12) \[\mathrm{FeOH}^{+}+\mathrm{H}^{+} \rightarrow\mathrm{Fe}^{2+}+\mathrm{H}_{2}\mathrm{O}\] (13) \[\mathrm{Fe}+2\mathrm{Cl} \rightarrow\mathrm{Fe}\mathrm{Cl}_{2}+2\mathrm{e}^{-}\] (14) \[\mathrm{FeCl}_{2}+\mathrm{Cl}^{-} \rightarrow\mathrm{Fe}\mathrm{Cl}_{3}+\mathrm{e}^{-} \tag{15}\]  
The ferrous chloride formed on the steel surface shown in equation (14) cannot stay longer on the surface and gets converted into an interface before getting dissolved in the solution by leaving the surface.