Structure effect of some amine derivatives on corrosion inhibition efficiency for carbon steel in acidic media using electrochemical and Quantum Theory Methods

Preparation of novel compounds, characterization and studying experimentally and theoretically as inhibitors through thermodynamic and quantum chemistry

“…This explains that inhibition efficiency has been increased with the increase of electron-donating ability. In another words, the ΔN values correlates strongly with experimental inhibition efficiency, hence the highest fraction of electrons transferred is associated with inhibitor which has the least efficiency (A2), while the least fraction of electrons transferred is associated with the inhibitor which has the best efficiency (A1) [3,54]. If the value of ΔEBack-donation < 0 and value of global hardness η > 0, this implies that charge transfer to a molecule followed by a back-donation from the molecule, hence it is possible to compare the stabilization among inhibiting molecules, the interaction will be occurred with same metal, then global hardness decreases.…”

“…Furthermore, DFT is considered a very useful technique to analyse the experimental data, thus in the present investigation, the quantum chemical has been calculated by using density functional theory for explaining the experimental results obtained and to further give insight into the inhibitors action of compounds A1 and A2 on the mild steel surface [52,53]. On the other hand, the quantum chemical results show ability of molecular structure for donation and back donation between the molecule and the metal surface [3]. Quantum parameters of heterocyclic compounds included EHOMO, ELUMO, S, ΔEgap, ΔN, ω, χinh, ƞinh, μ and ΔEBack-donation.…”

“…Also the positive values of EHOMO indicate to the ability of inhibitors to adsorb on the mild steel, and the type adsorption is chemisorptions [1,3,6]. Frontier molecular orbital theory is useful and important in predicting adsorption centers of the inhibitor molecules responsible for the interaction with metal surface atoms.…”

“…The LUMO is the orbital that could act as the electron acceptor since it is the innermost (lowest energy), in other words it is orbital that has room to accept electrons. ΔEBack-donation is directly proportional to the hardness (ƞ) of the molecule, and calculated as indicated in Equation 19 [3,54].…”

“…Through looking at the distribution of LUMO in Figure 15 it was noted that molecule of A1 inhibitor can easily accept electrons from the occupied 4s-orbital of Fe atoms by the benzene ring, oxygen atoms and nitrogen atoms to form binding forces between the inhibitor molecule and Fe atoms on the mild steel surface, while molecule of A2 inhibitor can easily accept electrons of occupied 4s-orbital of Fe atoms by nitrogen atom and two sulfur atoms. Consequently this electronic acceptance could help to formation more stable bonds between inhibitor molecules and surface of mild steel [3,25,35,[58][59][60][61][62].…”