## 3 Results and Discussion
### Discussion on Corrosion Inhibitors Comparison
\[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]0  
The cyclic voltammograms of calcium nitrite group are exhibited in \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]1 In comparison with Figures 8 and 10, chloride introduced corrosion reductions, which was demonstrated by the re-appearance of the wide passivation interval between A1 and A2. This result proves that organic corrosion inhibitor was conducive to passive film generation. It was mainly induced by the continuous adsorption process of TEA and the formation of protective film, blocking the contact of chloride ions with steel bars. TIPA had the same effect, to some extent. Moreover, the TIPA could combine with chloride and lead to the reduction in free chloride in the SCP solution, thereby decreasing the attack risk on passive film by chloride irons [53]. It was also reported that the organic corrosion inhibitor has a more excellent anti-corrosion effect compared with calcium nitrite [20]. \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]2 Cyclic voltammograms (1 st and 5 th cycles) in SCP solution with calcium nitrite. The voltammogram for the inorganic corrosion inhibitor group is demonstrated in \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]3 It was shown that cathodic potential peaks A1, A2, and A3 appeared in the voltammograms, as well as reduction peaks C1 and C2, due to the generation of Fe\({}^{3+}\). Significantly, a new cathodic potential peak appeared on the voltammograms, coded as A4, reflecting further formation of Fe. It is an additional reaction to form extra protective film after the formation of passive film, which is associated with the formation of FePO\({}_{4}\)[54] and Fe(MoO\({}_{4}\))\({}_{3}\)[50; 55], according to Equations (10) and (11). Nevertheless, this protection did not work for a long time because the thin layer is easy to be attacked [19]. \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]4  
\[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]5  
The voltammogram for the multi-component corrosion inhibitor group is shown in \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]6 The compound substance integrates the advantages of organic and inorganic compounds, which was the re-appearance of the wide passivated interval and the appearance of cathodic potential peak A4 [56]. Moreover, the current density of corresponding curves between cathodic potential peaks A1 and A2 were lower than that of same position shown in \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]7 It proves that passive film developed continuously due to the compound effect, overcoming the insufficient protection capacity of the protective film formed by inorganic corrosion inhibitors [57; 58]. Meanwhile, according to the results illustrated in Section 3.2, the addition of inorganic components is also a benefit for the promotion of change transfer resistance. In summary, the anti-corrosion effectiveness of the multi-component corrosion inhibitor was confirmed, and its mechanism has also been interpreted by various experimental techniques. \[\mathrm{Fe}+2\mathrm{OH}^{-}\leftrightarrow\mathrm{Fe(OH)}_{2}+2\mathrm{e}^{-} \tag{2}\]8 Cyclic voltammograms (1 st and 5 th cycles) in SCP solution with organic corrosion inhibitor.