Functional Pyromellitic Diimide as a Corrosion Inhibitor for Galvanized Steel: An Atomic-Scale Engineering

Abstract

Corrosion of metal/steel is a major concern in terms of safety, durability, cost, and environment. We have studied a cost-effective, nontoxic, and environmentally friendly pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel through density functional theory. An atomic-scale engineering through the functionalization of PMDI is performed to showcase the enhancement in corrosion inhibition and strengthen the interaction between functionalized PMDI (F-PMDI) and zinc oxide (naturally existing on galvanized steel). PMDI is functionalized with methyl/diamine groups (inh1 (R = -CH3, R? = -CH3), inh2 (R = -CH3, R? = -CH2CH2NH2), and inh3 (R = -C6H3(NH2)2, R? = -CH2CH2NH2). The corrosion inhibition parameters (e.g., orbital energies, electronegativity, dipole moment, global hardness, and electron transfer) indicate the superior corrosion inhibition performance of inh3 (inh3 > inh2 > inh1). Inh3 (?182.38 kJ/mol) strongly interacts with ZnO(101� 0) compared to inh2 (?122.56 kJ/mol) and inh1 (?119.66 kJ/mol). The superior performance of inh3 has been probed through charge density and density of states. Larger available states of N and H (of inh3) interact strongly with Zn and Osurf (of the surface), respectively, creating N-Zn and H-Osurf bonds. Interestingly, these bonds only appear in inh3. The charge accumulation on Osurf, and depletion on H(s), further strengthens the bonding between inh3 and ZnO(101� 0). The microscopic understanding obtained in this study will be useful to develop low-cost and efficient corrosion inhibitors for galvanized steel. � 2022 American Chemical Society.