## 3 Results and Discussion
### Raman Spectroscopy Analysis  
The Raman spectra of the mild steel panels after subjection to WSS for 96 h, in the presence of inhibitors or not, are depicted in Figure 11. The corresponding classification of the Raman spectra peaks is in Table S1. Regarding the _Steel-WSS-blank_, it can be mentioned that the region between 200 and 450 cm\({}^{-1}\) of the Raman graph belongs to \(\alpha\), \(\beta\), and \(\gamma\)-crystalline iron oxides and oxyhydroxides, accompanied with amorphous products, but is not considered as appropriate for the precise identification of the rust compounds (Figure 11a). Quite guardedly, it could be claimed that the pair of peaks near 225 and 290 cm\({}^{-1}\) is assigned to the presence of hematite, the peak near 298 cm\({}^{-1}\) is assigned to the presence of goethite, and that around 663 cm\({}^{-1}\) is assigned to the presence of magnetite [66]. The pair of peaks with the shoulders at about 1320 and 1630 cm\({}^{-1}\) is attributed to ferrihydrites, which is the main iron oxyhydroxic rust compound of the present system [7]. Taking into account the Raman spectrum of _Steel-WSS-Na2 HPO4_ (Figure 11b), it may be remarked that except for the initial noisy fluctuations from iron oxyhydroxics and oxides [63; 67] or either from Fe-O lattice vibrations [68], the most intense peak at about 1310 cm\({}^{-1}\) arrives from iron phosphate species and may be addressed to PO2 asymmetric stretch [69], whereas the less intense (accompanied with a shoulder) near 1600 cm\({}^{-1}\) could be attributed to bending vibrations of water molecules [68] attached to the more hygroscopic phases. Considering the _Steel-WSS-MBT_, it can be mentioned that the organic inhibitor adsorption on [Fe-O-OH] species mitigated their characteristic Raman shifts, assuming that the elevated experimental line in the region 200-400 cm\({}^{-1}\) implies their presence under MBT (Figure 11c). The two most discrete peaks were captured near 1380 cm\({}^{-1}\) and 1590 cm\({}^{-1}\) with a neck between them, which was a shifted pattern that was commented previously to emerge due to ferrihydrites. Furthermore, it could be claimed that the pair of peaks at 220 and 290 cm\({}^{-1}\) with the detection of the primarily lower peak near 700 cm\({}^{-1}\) is related to pyrite characteristic Raman shift, meaning the identification of the Fe-S band [70]. Enhancing this option, it should be considered that after drying at specific areas, the organic voluminous MBT molecule would be detected, hiding the rest, more crystalline structures underneath, whereas there would be sites where the organic layer would have been partially detached. Figure 11: Raman spectra of the mild steel panels after subjection in WSS for 96 h: (**a**) _Steel–WSS–blank_, (**b**) _Steel–WSS–Na2 HPO4_, (**c**) _Steel–WSS–MBT_, (**d**) _Steel–WSS–Na2 HPO4_–MBT_. In view of the _Steel-WSS-Na2 HPO4-MBT_ Raman spectrum, it can be said that despite the fact that the first peak at 1050 cm\({}^{-1}\) seems to be attributed to bending vibrations of C-H bands of the MBT aromatic ring [65], its emergence in combination with the shoulder up to the next peak around 1185 cm\({}^{-1}\) and the smaller peak at 1316 cm\({}^{-1}\) reveal the identification of iron phosphate crystalline or amorphous compounds [69] (Figure 11d). The latter peak at 1628 cm\({}^{-1}\) is believed to correspond to the thione mode of the MBT molecule, which is indicative of being perpendicular to the metal surface orientation of the aromatic ring [65]. The Raman spectra of the mild steel panels after exposure to 3.5 wt % NaCl for 96 h, in the presence of inhibitors or not, are illustrated in Figure 12. Regarding the _Steel-NaCl-blank_, it can be mentioned that the generated thick three-dimensional amorphous corrosion products and the most dense and stable generated passive layer on the mild steel measured surface are considered to hinder the detection of the Raman shifts of more crystalline phases beneath (Figure 12a).