## 3 Results and Discussion
### Corrosion Inhibition Mechanism
#### 3.5.2 Corrosion Inhibitors
However, the duration of each stage and even of the whole adsorption process and the enhanced stability and uniformity of the final layer imply that a more complicated process had actualized. It was found that MBT has the tendency to form hydrophobic bonds in neutral aquatic electrolytic solutions [103], followed by a self-assembly ordering with characteristic duration [104]. In case of parallel plane geometry to the metallic surface, hydrophobic-originating complexes create locally hydrophobic complexes as metal islands that combine afterwards to a uniform protective layer. In perpendicular orientation, similar mechanisms with hydrophobic intermolecular connections were suggested [65]. Despite the appearing complexity of the adsorption process of MBT, its kinetics were already specified and recorded in the literature, as also the self-assembly process through which the inhibitor lays the protective layer [29; 65]. At a second glance, a precise orientation of the planar organic inhibitor could be similar to that proposed in the study of [PERSON] et al. on the Ag surface [72]. Due to the increased local electronic density and the negative \(\delta\) contribution on the thiol edge, in conjunction with a commonly observed attitude of S to alter the planarity of MBT-thione [100; 105] and bend the S-C bond [103], it seems as the most probable scenario that the inhibitor attaches onto a mild steel surface, with the exocyclic sulfur-carbon bond perpendicular to metal and the remainder planar molecule angled [65]. In that way, the imminent rearrangement process, which initiates the self-assembly of the protective layer, would lack steric hindrance, as each molecule-plane could be simultaneously strongly chemically bonded onto the metal through an exocyclic sulfur atom. On the other hand, the slightly negatively charged remainder planes would be free to rotate, providing a relevant ionic permeability to the protective layer and diminishing the possibility for the layer rupture. Phosphorus consists of a significant alloying element of low-alloyed and carbon steels against atmospheric corrosion [106] and Cl\({}^{-}\) attack [107], and it is considered to improve machinability, fatigue, and hardenability. Phosphating through immersion baths, as conventionally realized in industry, is considered to be complete after several days, mainly due to recrystallization and solid-state transformation processes and in order to enhance surface coherence with metallic coatings, as zinc phosphating [53] and even with organic protective coatings. There has been a variety of chiefly organic substances proposed as accelerators of phosphating, such as certain amines, pyridines, and other oxidizing substances [108]. Phosphate anions have been considered to confer satisfying corrosion resistance, stabilizing both crystalline and amorphous phases in the corrosion product layer [109]. Although inorganic phosphorus-containing compounds were broadly utilized against the corrosion and wear phenomena of mild steel, and its crystallization kinetics and pathways were intricately investigated in ambient conditions [110], there are impenetrable aspects to explore up to date, from the interatomic to hypercrystallic level. Not only does phosphorus bind strongly to common non-metals such as oxygen and nitrogen, it also does so with metals and minerals consisting of oligomeric or near-polymeric complexes, such as ferrates and polyoxometallates. In phosphate tetrahedra, the phosphorus is strongly bonded to oxygen atoms, and their bond length could found to be even fourfold inside the same solid (bond-stretch isomerism) [59; 110]. In particular, inorganic phosphate tetrahedra (mainly PO4\({}^{3-}\), HPO4\({}^{2-}\)) behave as relatively strong Lewis bases, maintain their bonding in aquatic near-neutral solutions, and precipitate forming insoluble salts with the locally available cations (Figure 24b).