## 3 Results and Discussion
### Discussion on Corrosion Inhibitors Comparison  
Corrosion resistance of different types of corrosion inhibitor are listed in Table 4. The inhibitors are classified as organic, inorganic, or composite corrosion inhibitors. The inhibition efficiency of our studied multi-component corrosion inhibitors reached 95.3% [27], and the OCP and Rct values reached \(-\)0.38 V and 932.19 k\(\Omega\cdot\)cm\({}^{2}\), respectively. The test results given in these studies are compared to the relevant values correlated with multi-component corrosion inhibitors because different test methodologies are utilized to detect steel corrosion in different papers. It can be found that the inhibition efficiency and change transfer resistance of these organic inhibitors are generally lower than that of used in this research. The inorganic inhibitors listed in the table lead to \(-\)0.4 V of OCP value, which is still not up to the level of inorganic corrosion inhibitor used in this work. The means of selecting MFP and T-4 as inorganic components in this research could provide better protecting effects. The composite corrosion inhibitors illustrated in Table 4 exhibit excellent anti-corrosion efficiency, and the IE value of these inhibitors reaches up to 95%. Compared with the composite inhibitors listed in the table, our studied corrosion inhibitor also reached the same level, which is reflected in the high IE values. As for the testing methods, both common methods, such as OCP and EIS, and unique methods including potentiodynamic polarization and XPS were used to detect the steel bar interface characteristic and molecular structures of the corrosion inhibitors. However, these methods explored the mechanism in the perspective of electrochemistry, which is a static state reaction process that occurs on steel bar surfaces that cannot be analyzed. As a dynamic non-destruction measurement, CV is usually used to detect oxidation-reduction reactions among the interface of metal. Thus, we attempt to explore the mechanism of multi-component corrosion acts on steel bar surfaces by cyclic voltammetry (CV). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**No.** & **Corrosion Inhibitor** & **Classification** & **Cl\({}^{-}\) Concentration** & **Test Methods** & **IE/Best Values** & **Refs.** \\ \hline \multirow{5}{*}{1} & N-(n-octyl)-3 & \multirow{5}{*}{Organic inhibitor} & \multirow{5}{*}{3.5\% NaCl, pH 1.5} & OCP, Tafel Polarization, & \multirow{5}{*}{85.1\% (IE)} & \multirow{5}{*}{[41]} \\  & methylpyridin & & & & & \\  & bromide (Py12) & & & & & \\ \hline \multirow{2}{*}{2} & \multirow{2}{*}{Imidazoline} & \multirow{2}{*}{Organic inhibitor} & \multirow{2}{*}{32.107 g/L NaCl, pH 6.3} & \multirow{2}{*}{Polarization curve, EIS} & \multirow{2}{*}{67\% (IE)} & \multirow{2}{*}{[42]} \\  & & & & & & \\ \hline \multirow{3}{*}{3} & \multirow{3}{*}{3-sulphinyalkyl-5-amino-1H-1,2,4-triazole} & \multirow{3}{*}{Organic inhibitor} & \multirow{3}{*}{1\% HCl solution} & EIS, Accelerated & \multirow{3}{*}{115.01 k\(\Omega\cdot\)cm\({}^{2}\)} & \multirow{3}{*}{[43]} \\  & & & & & & \\ \cline{1-1} \cline{5-5}  & & Corrosion Test, & & & (Rp, EIS) & \\ \hline \multirow{2}{*}{4} & Migratory corrosion inhibitors (MCLs) & \multirow{2}{*}{Organic inhibitor} & \multirow{2}{*}{3.5\% NaCl, pH 12.3} & EIS, Tafel curve & \multirow{2}{*}{9.94 k\(\Omega\cdot\)cm\({}^{2}\)} & \multirow{2}{*}{[44]} \\ \cline{1-1} \cline{5-5}  & Organic compound-based corrosion inhibitor & \multirow{2}{*}{Organic inhibitor} & \multirow{2}{*}{brackish water} & EIS, Tafel curve & \multirow{2}{*}{99.3\% (IE)} & \multirow{2}{*}{[45,46]} \\ \cline{1-1} \cline{5-5}  & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of multi-component corrosion inhibitors over other (including organic and inorganic) corrosion inhibitors.