## 3 Results and Discussion
### Corrosion Protection Evaluation
#### 3.2.4 Corrosion Inhibition Mechanism  
Taking into consideration the aforementioned results together with our previous studies on mild steel corrosion protection [16], the following corrosion inhibition mechanism can be assumed. Briefly, considering the corrosion mechanism of iron, the exposure of mild steel into saline corrosive environment results in the release of ferrous ions (Fe\({}^{2+}\)) and ferric ions (Fe\({}^{3+}\)) ions due to iron oxidation (anodic part), as depicted in reactions 4 and 5. It should be mentioned that in the pH range from 6.92 to 7.74 where the measurements were conducted, there was a reduction in the dissolved O\({}_{2}\) to OH\({}^{-}\) ions (reaction 6) that acted as the cathodic part. The produced OH\({}^{-}\) reacted with the Fe\({}^{2+}\)or Fe\({}^{3+}\), and iron hydroxides were synthesized (reactions 7, 8) and precipitated onto the corroded metal surface creating a thick gel that is characteristic of wet rapid corrosion [58]. \[\text{Fe}\rightarrow\text{Fe}^{2+}+2\text{e}^{-},\text{anode} \tag{4}\]  
\[\text{Fe}\rightarrow\text{Fe}^{3+}+3\text{e}^{-},\text{anode} \tag{5}\]  
\[\text{O}_{2}+2\text{H}_{2}\text{O}+4\text{e}^{-}\to 4\text{OH}^{-}, \text{cathode} \tag{6}\]  
\[\text{Fe}^{+2}+2\text{OH}^{-}\rightarrow\text{Fe(OH)}_{2}(\text{s}), \tag{7}\]  
\[\text{Fe}^{+3}+3\text{OH}^{-}\rightarrow\text{Fe(OH)}_{3}(\text{s}), \tag{8}\]  
In aqueous NaCl(aq) solution, the presence of Cl\({}^{-}\) also reacts with the iron cations according to the reactions 9 and 10 forming intermediate compounds. Then, these compounds react with water producing highly soluble iron hydroxide compounds and HCl (reactions 11, 12) [1]. Furthermore, the reaction between iron oxides and hydroxides causes the production of another thick gel, [Fe-O-OH], that can further react with iron cations giving additional types of iron oxides that mainly consist of magnetite (Fe\({}_{3}\)O\({}_{4}\)) (reaction 13). \[\text{Fe}^{+2}+2\text{Cl}^{-}\rightarrow\text{FeCl}_{2}, \tag{9}\]  
\[\text{Fe}^{+3}+3\text{Cl}^{-}\rightarrow\text{FeCl}_{3}, \tag{10}\]  
\[\text{FeCl}_{2}+2\text{H}_{2}\text{O}\rightarrow\text{Fe(OH)}_{2}(\text{s})+2 \text{HCl}, \tag{11}\]  
\[\text{FeCl}_{3}+3\text{H}_{2}\text{O}\rightarrow\text{Fe(OH)}_{3}(\text{s})+3 \text{HCl}, \tag{12}\]  
\[8\text{FeOOH}+\text{Fe}^{2+}+2\text{e}^{-}\to 3\text{Fe}_{3}\text{O}_{4}+4 \text{H}_{2}\text{O}, \tag{13}\]  
The formatted magnetite passive film can be deteriorated by the attack of the Cl\({}^{-}\) provoking several corrosion phenomena [59]. The corrosion protection effectiveness of ATT can be attributed to its chemisorption onto the mild steel surface, decreasing the dissolution rate of the metal because of an adherent passive film formation [60]. As it was discussed in our previous work [16], the ATT corrosion inhibitor hasan enhanced binding capability to be attached onto the metal surface due to the presence of both nitrogen and sulfur atoms. The reason is that both these elements can act as electron donors [43; 61]. This tendency is further increased by the presence of heterocyclic rings on the inhibitor molecule [61; 62] and the corresponding resonance existence [63]. According to the work of [PERSON] et al. [64], the ATT can be represented by the tautomers of Figure 11; whereas the thion form predominantly exists. The thion form of ATT can form a stable layer onto the steel surface due to chemical adsorption [65]. Figure 12 illustrates the schematic representation of the chemical adsorption of the thion form of ATT onto the surface of the mild steel. It can be seen that a layer of iron oxides was formed onto the steel surface due to its interaction with the environment. The ATT molecules chemically bonded onto this layer. Taking into account the obtained results that were supported with the aforementioned mechanism along with our previous studies on the corrosion behavior of mild steel [16], it may be remarked that the chemical compounds including sulfur and nitrogen atoms can be considered as corrosion inhibitors.