7. Corrosion inhibitors studied using MD

Feng et al. [74] performed the MD simulation of 1-[N,N0 -bis (hydroxylethylether)- aminoethyl]-2-stearicimidazoline (HASI). The MD calculation suggests that adsorbed imidazoline molecule is parallel to the iron surface in order to maximize its contact with the surface (Figure 5). The interaction energy for Fe atom is �284 kJ/mol, for Fe3O4 is �226 kJ/mol and for Fe2O3 is �157 kJ/mol. So, inhibitor adsorbed on Fe surface more strongly than Fe3O4 and Fe2O3.

MD calculation of adsorption of indazole (IA) and 5-aminoindazole (AIA) on copper surface was studied Qiang et al. [79]. The optimized equilibrium configuration of inhibitors molecules are shown in Figure 6 and inhibitors adsorption occurs through parallel orientation. The adsorption energy between Cu (1 1 1) surface and inhibitor molecule are �250.86 kJ/mol for IA and �307.86 kJ/mol for AIA.

Molecular level MD calculation of Benzotriazole and Phospono derivatives was studied by Kaya et al. [78] on aluminum surface. The best adsorption configuration of inhibitor molecules on Al (111) surface are represented in Figure 7. The parallel configuration of inhibitor molecules suggests the stronger adsorption.

8. Conclusion and future work

(g and h) on Al (1 1 1) surface. Top: top view and bottom: side view [78].

optimization (inset images show the on-top views) [79].

DOI: http://dx.doi.org/10.5772/intechopen.84126

Figure 6.

Figure 7.

133

Computational program provide an atomistic view for understanding the corrosion inhibition process and significantly contribute for the selection of adequate inhibitor molecules. DFT calculations has made possible to characterize a suitable inhibitor molecules using their intrinsic properties such as energies of HOMO and LUMO orbitals, energy gap (ΔE), electronegativity, hardness, softness, etc. It helps corrosion scientist to understand the inhibitor-metal interaction through the locations of HOMO and LUMO orbitals. The examination of local reactivity reveals the

Equilibrium adsorption configuration of inhibitors PBTA (a and b),TBTA (c and d), BPA (e and f), PAA

Equilibrium adsorption configuration for IA and AIA on Cu (111) surface in 3% NaCl solution after

Investigation of Corrosion Inhibitors Adsorption on Metals Using Density Functional Theory…

nucleophilic and electrophilic centers which react with the metal surfaces. The literature survey suggests that with help of quantum chemistry a good understanding of corrosion system can be achieved when various metal surfaces and various inhibitor molecules are compared. DFT has ability to perform

Figure 5.

Adsorption of imidazoline molecule on (a) Fe, (b) Fe3O4 and (c) Fe2O3 surfaces. The left is top view, and the right is side view [74].

Investigation of Corrosion Inhibitors Adsorption on Metals Using Density Functional Theory… DOI: http://dx.doi.org/10.5772/intechopen.84126

#### Figure 6.

Khalid and Madkour et al. [13, 80, 81] probe the interactions between benzotriazole, methionine, phenol derivatives and copper via quantum calculations respectively. The obtained results suggests that quantum parameters are very useful

(hydroxylethylether)- aminoethyl]-2-stearicimidazoline (HASI). The MD calculation suggests that adsorbed imidazoline molecule is parallel to the iron surface in order to maximize its contact with the surface (Figure 5). The interaction energy for Fe atom is �284 kJ/mol, for Fe3O4 is �226 kJ/mol and for Fe2O3 is �157 kJ/mol.

MD calculation of adsorption of indazole (IA) and 5-aminoindazole (AIA) on copper surface was studied Qiang et al. [79]. The optimized equilibrium configuration of inhibitors molecules are shown in Figure 6 and inhibitors adsorption occurs through parallel orientation. The adsorption energy between Cu (1 1 1) surface and

Molecular level MD calculation of Benzotriazole and Phospono derivatives was studied by Kaya et al. [78] on aluminum surface. The best adsorption configuration of inhibitor molecules on Al (111) surface are represented in Figure 7. The parallel

Adsorption of imidazoline molecule on (a) Fe, (b) Fe3O4 and (c) Fe2O3 surfaces. The left is top view, and the

So, inhibitor adsorbed on Fe surface more strongly than Fe3O4 and Fe2O3.

inhibitor molecule are �250.86 kJ/mol for IA and �307.86 kJ/mol for AIA.

configuration of inhibitor molecules suggests the stronger adsorption.


in characterizing organic compounds as an adsorbate.

Feng et al. [74] performed the MD simulation of 1-[N,N0

7. Corrosion inhibitors studied using MD

Corrosion Inhibitors

Figure 5.

132

right is side view [74].

Equilibrium adsorption configuration for IA and AIA on Cu (111) surface in 3% NaCl solution after optimization (inset images show the on-top views) [79].

#### Figure 7.

Equilibrium adsorption configuration of inhibitors PBTA (a and b),TBTA (c and d), BPA (e and f), PAA (g and h) on Al (1 1 1) surface. Top: top view and bottom: side view [78].

#### 8. Conclusion and future work

Computational program provide an atomistic view for understanding the corrosion inhibition process and significantly contribute for the selection of adequate inhibitor molecules. DFT calculations has made possible to characterize a suitable inhibitor molecules using their intrinsic properties such as energies of HOMO and LUMO orbitals, energy gap (ΔE), electronegativity, hardness, softness, etc. It helps corrosion scientist to understand the inhibitor-metal interaction through the locations of HOMO and LUMO orbitals. The examination of local reactivity reveals the nucleophilic and electrophilic centers which react with the metal surfaces.

The literature survey suggests that with help of quantum chemistry a good understanding of corrosion system can be achieved when various metal surfaces and various inhibitor molecules are compared. DFT has ability to perform

calculations for complex or large organic molecules that can be applied as a potential corrosion inhibitor. In addition, DFT provide a platform to scientist for designing a unique inhibitor molecule and understand their molecular structure at atomistic level.

References

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DOI: http://dx.doi.org/10.5772/intechopen.84126

dynamics and Monte Carlo simulations as powerful tools for study of interfacial adsorption behavior of corrosion inhibitors in aqueous phase: A review. Journal of Molecular Liquids. 2018;260:

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In recent years, computational modeling like DFT and MD provide real inhibitor-metal interaction picture by performing calculation in aqueous phase. Such an approach act as a benchmark for experimental study in the field of corrosion research.

Molecular dynamic simulation (MD) gives a representative image of inhibitor molecule orientation on the metal surface. This helps to analyze the inhibition activity of inhibitor molecules, i.e., inhibitor with parallel or flat orientation with respect to metal surface will cover more surface area and provide a better corrosion inhibition protection as compared to the inhibitor which have vertical orientation.

Future research includes modeling the electrochemical potential, generation of alloy surface layers, addition of thin oxide film covering onto the metal surface, calculation of more complex molecule, comprehension of solvent molecule role in adsorption, understanding the defect role in adsorption process, etc.
