Coumarin as a green inhibitor of chloride-induced aluminum corrosion: theoretical calculation and experimental exploration

Abstract

The corrosion inhibition mechanism of coumarin in a chloride-containing environment.

Impact of Aqueous Extract Artemisia Herba-Alba Leaves as a Green Inhibitor against Acid Activation of 2024 Aluminum Alloy

“…Val, Deox, Isos, and Isof all contain O and/or N groups and therefore can bind with Al 3+ ions. Tis agrees well with previous results showing the formation of Alcoumarin [74] at the metal surface exposed to a chloride solution. Besides, favonoids coordinate Al ions in their neutral form (their form in acidic conditions) via the α-hydroxycarbonyl site (Figure 12) [79].…”

“…From Figure 14, it is seen that the HOMO and LUMO of Val and Deox are both localized on the oxygen of carbonyl while the HOMO and LUMO in Isof and Isos have diferent locations. Te HOMO location of Isof is the O lone pair of the C�O which corresponds to the same adsorption site identifed by Tan et al [74] with coumarin. Te E HOMO values for the four structures tested are almost the same which suggests a comparable tendency to donate electrons to the metal surface through its HOMO.…”

“…Valine was reported to inhibit the corrosion of Al in an acidic solution but less efciently than amino acids with sulfur atom or aromatic groups [73]. On the other hand, coumarin is a mixed-type inhibitor for Al in a neutral chloride solution [74], artemisinin has been already reported to be a good inhibitor of mild steel in an H 2 SO 4 solution [75], and favonoids are phenolic derivatives containing polar groups that enhance the adsorption on the metal surface [76]. Val, Deox, Isof, and Isos are therefore potential inhibitors, and dft analyses were conducted to evaluate and compare the types of interactions and their ability to adsorb to the metal surface.…”

“…Tis agrees with the results of Tan et al which showed that electron donation occurred from the aluminum surface to coumarin (with a structure close to Isof ). [74] In comparison, Val and Deox can donate electrons to the Al surface but cannot receive donated electrons from the Al surface in return. Te donation of electrons from the HOMO and the backdonation of electrons from the metal to the LUMO can be benefcial for a high inhibition efciency of Isos and Isof.…”