## 3 Results and Discussion
### Corrosion Resistance Performance
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Formulation**} & **W\% of** & **R\({}_{\rm p}\)** & **r\({}_{\rm v}\times 10^{-8}\)** & **C\({}_{\rm H}\times 10^{-7}\)** & **\(\rm\tau\)** & **\(\rm\tau\)** & **f\({}_{\rm max}\)** & **\% IE** \\  & **Inhibitor** & **(\(\rm\Omega\) cm\({}^{2}\))** & **n** & **(\(\rm\Omega\)- 1 5 5 5 \(\rm cm^{-2}\))** & **(\(\rm\Omega\)- 1)** & **(\(\rm\Omega\)- 2)** & **(\(\rm\Omega\)- 3)** & **(\(\rm\Omega\)- 4)** \\ \hline Alkyd & - & 577.2 & 0.5707 & 7.598 & 1.04 \(\times\) 10\({}^{3}\) & 0.67 & 236.69 & - \\ \hline \multirow{4}{*}{\(\rm Fe_{3}O_{4}\) MNPs} & 5 & 986.1 & 0.4287 & 10.437 & 5.23 & 0.12 & 1263.7 & 41 \\  & 10 & 1073 & 0.5286 & 0.024 & 2.79 \(\times\) 10\({}^{3-}\) & 0.02 & 541.2 & 46 \\  & 15 & 1143 & 0.7363 & 0.022 & 7.94 & 0.18 & 856.72 & 50 \\  & 20 & 1235 & 1.201 & 0.001 & 1.76 \(\times\) 10\({}^{3}\) & 0.21 & 734.38 & 53 \\  & 25 & 1304.7 & 1.079 & 0.004 & 1.06 \(\times\) 10\({}^{3}\) & 0.10 & 1508 & 56 \\ \hline \multirow{4}{*}{\(\rm Poly(aniline-co-o-toluidine)/Fe\({}_{3}\)O\({}_{4}\)]} & 5 & 1167 & 1.294 & 0.026 & 6.98 \(\times\) 10\({}^{4}\) & 0.61 & 258.61 & 50 \\  & 10 & 1195 & 0.1138 & 5.117 & 1.64 \(\times\) 10\({}^{-28}\) & 7.96 & 20.934 & 52 \\ \cline{1-1}  & 15 & 2651 & 0.2900 & 1.158 & 3.58 \(\times\) 10\({}^{-8}\) & 3.90 & 40.792 & 78 \\ \cline{1-1}  & 20 & 2810 & 0.6795 & 0.039 & 1.31 & 2.77 & 23.365 & 80 \\ \hline MNPs & 25 & 2749 & 0.8284 & 0.040 & 68.7 & 0.39 & 404.57 & 79 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The EIS parameters for the coated alloy in the presence of [poly(aniline-co-o-toluidine)/Fe\({}_{3}\)O\({}_{4}\)] MNPs and magnetite with alkyld paint in 0.1 mol/L HCl at 298 K.  
combined with magnetic nanoparticles, effectively impeding the penetration of corrosive particles, such as water molecules, oxygen, and other ions [60]. A higher percentage of corrosion inhibitor improves the inhibitory efficiency. The values of R\({}_{\rm p}\) also rise with an increased percentage of Fe\({}_{3}\)O\({}_{4}\) MNPs and [Poly(aniline-co-o-toluidine)/Fe\({}_{3}\)O\({}_{4}\)] MNPs, as indicated in Table 3. This elevation in R\({}_{\rm p}\) values results in a corrosion reduction and efficiency augmentation [61]. However, a decreased inhibitory efficiency may be noticed at certain inhibitor weight percentages, due to the potential deterioration of the coating layer caused by surface roughness, heterogeneity, and possible structural deformation [62]. The adsorption of the Fe\({}_{3}\)O\({}_{4}\) inhibitor and the copolymer [Poly(aniline-co-o-toluidine)/Fe\({}_{3}\)O\({}_{4}\)] MNPs on the corroded alloy surface impedes charge transport, and obstructs corrosion-prone active sites, leading to an R\({}_{\rm p}\) increase from 577.2 k\(\Omega\) cm\({}^{2}\) (with the alkyld alone) to 1304.7 and 2749 k\(\Omega\) cm\({}^{2}\) (with 25 wt.% of Fe\({}_{3}\)O\({}_{4}\) and the copolymer [Poly(aniline-co-o-toluidine)/Fe\({}_{3}\)O\({}_{4}\)] MNPs, respectively). This significant effect contributes to a substantial corrosion rate reduction, thus providing effective protection for the steel surface. The data displayed in Table 3 exhibit a substantial reduction in C\({}_{\rm dl}\) (double layer capacitance) values upon application of the treated coatings, compared to using alkyld resin alone. This indicates that the incorporated inhibitors, both magnetite and [copolymer/Fe\({}_{3}\)O\({}_{4}\)] MNPs, are effective in hindering the corrosion rate of alloys by implementing an adsorption mechanism, and thereby mitigating the extent of metal dissolution. The decreased C\({}_{\rm dl}\) values associated with the highest percentages of both magnetite and [copolymer/Fe\({}_{3}\)O\({}_{4}\)] MNPs can be attributed to a lower dielectric constant, and an increase in the double layer thickness, due to the adsorption of these particles on the carbon steel surface.