## 4 Conclusions  
Our study provides a comprehensive exploration into the corrosion inhibitor properties of alkanolammonium salts, with a particular focus on EEA4 NB, utilizing a combined electrochemical and computational approach on carbon steel in a 3% NaCl solution. Our experimental findings highlight the notable corrosion inhibition capabilities of EEA4 NB on carbon steel electrode surfaces in saline solutions, especially at a concentration of \(5\times 10^{-3}\) mol\(\cdot\)L\({}^{-1}\), achieving an inhibition efficiency of up to 96%. The use of potentiodynamic polarization curves and electrochemical impedance spectroscopy has offered valuable insights, unraveling the intricate dynamics at the interface during the inhibition process. Quantum chemical calculations further strengthen our conclusions, affirming the anion's superiority in inhibition efficiency due to its highest HOMO and lowest energy gap when compared to EEA4 NB and cations. This integrated approach enhances our understanding of the inhibitory mechanisms and underscores the potential applications of alkanolammonium salts as effective corrosion inhibitors for carbon steel in aggressive environments.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Inhibitor/Inhibitor Concentration** & **Medium** & **Jcorr \(\mu\)A/cm\({}^{2}\)** & **IE, \%** & **Adsoption Isotherm** & **Ref.** \\ \hline Ammonium salt of the sulfated fatty acid diethanolamine amide (AS)/50 ppm & 1\% NaCl & 31 & 92.0 & Langmuir & [42] \\ \hline Aminomethylene- phosphonate/4.9 mM & 3.5\% NaCl, pH = \(\sim\)3 & 4.03 & 87.99 & Langmuir & [20] \\ \hline Amino-alcohol-based mixed inhibitor (Ferrogard 903)/1 mL/50 mL water & 0.5 M NaCl, pH = 12.1 & 12,000 & - & - & [43] \\ \hline Phylanthus muellerianus leaf extract (2 g) and triethanolamine (6 g)/(C6H15 NO3: TEA) & 3.5 wt\% NaCl & - & 98 & - & [44] \\ \hline Aryl aminoalcohol/5 ppm & 0.3 M NaCl & 1.74 & 89.9 & Langmuir & [41] \\ \hline \(N\)-methyl-2-hydroxyethylamine (M-2 HEAOL) and bis-2-hidroxyethylamine (B-HEAOL)/5 mmol/L & 0.01 M NaCl & 0.12 & 97 & Langmuir & [40] \\ \hline Polyethyleneimine (PEI)/100 \(\upmu\)mol L\({}^{-1}\) & 3.5 \% NaCl & 10.9 & 86.54 & Langmuir & [45] \\ \hline EEA4 NB & 3\% NaCl & 0.145 & 96.6 & Langmuir & Present work \\ \hline \hline \end{tabular}
\end{table}
Table 5: Corrosion currents, inhibition efficiencies, and adsorption isotherms of different compounds on iron in various solutions.  
Author Contributions: Conceptualization N.P. and M.C.; investigation N.P., C.M. and Y.C.; writing--original draft N.P., M.C. and Y.C.; writing--review and editing N.P. and M.C. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy. Acknowledgments: This work was supported by Program No. 2 of the \"Coriolan Dragulescu\" Institute of Chemistry. Conflicts of Interest: The authors declare no conflicts of interest. References