## 3 Results and Discussion
### Corrosion Inhibition Mechanism
#### 3.5.1 The Main Pathway of Corrosion Process in an Fe-C/NaCl (aq) System
In particular, the identification of green rusts (LDH structures) in the obtained corrosion products denotes that ferric ion creation is favored. Moreover, as the forming Fe-Cl salts were expected to have been dissolved, and were considered totally soluble in the present aqueous system, the chlorides detection in the rust layer indicates that sulfate green rust structures could have captured chlorides [94,95,96]. After a relative stabilization of the double layer, with the inner layer to consist mainly of magnetite (Fe\({}_{3}\)O\({}_{4}\)), mass transfer, electromigration and more time-consuming phenomena take place, depending on the local physicochemical conditions and compounds concentrations. In the mere aqueous saline system of mild steel, it was expected that the Cl\({}^{-}\) would attack and damage the magnetite passive film, triggering a series of local corrosion phenomena, as analyzed in the aforementioned paragraph. Hence, as referred also in spectroscopic measurements, Cl\({}^{-}\) were not expected to be detected in solid phases, as they are very soluble in the current system [97]. Essentially, the generated Fe\({}^{2+}\) and e\({}^{-}\) from the mild steel dissolution in anode diffuse through the inner layer (or magnetite layer) and provoke the cathodic precipitation of magnetite, reducing the continuously forming oxyhydroxides according to reaction (9) and conferring a particular thickness to the bulk rust layer. In case of aeration or in the presence of a sufficient quantity of dissolved oxygen, for the wet condition, water and oxygen molecules pass through the FeO(OH) outer layer and oxidize magnetite, forming again stacking oxyhydroxides and interstitial species mainly of [Fe, O, OH], bonding with oxygen bridges and hydrogen bonds in a near-neutral environment (reaction (15)). \[\mathrm{3 Fe_{3}O_{4}}+3\mathrm{/4O_{2}}+9\mathrm{/2H_{2}O}\rightarrow\mathrm{9 FeOOH}, \tag{15}\]A more acceptable approximation for the latter would be the formation of Fe-OH-OH, which is more stable [44]. A significant variable is the surface charge of the outer FeO(OH) layer, depending on the protonation of Fe-OH-OH for a wet near-neutral environment, and deprotonation of the Fe-OH-OH layer in more acidic conditions. In the conventional natural mild steel saline system, the more time-consuming mechanisms and solid-state transformations are considered to proceed evermore, due to the thermodynamic equilibriums of each particular molecular interaction (aging). Characteristic processes of that stage are the further dehydration and crystallization of the oxyhydroxides and of the Fe(OH)\({}_{3}\), as previously observed even in wet conditions, underlying the outer rust layer. Additionally, complicated structures of crystalline flowers, honeycombs, nests, rods, and other unique formations emerge, as described elaborately in our SEM analysis, which were generated axially with regard to the metallic surface, as part of a family of processes that is responsible for illustrating the rust layer constitution for the most of the mild steel corrosion investigations in the past.