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

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Metal corrosion, particularly of steel, poses significant safety, durability, economic, and environmental challenges.
• Galvanized steel relies on a protective zinc oxide layer, which is susceptible to degradation.
• Developing effective, non-toxic, and sustainable corrosion inhibitors is crucial for extending material lifespan and reducing environmental impact.

Purpose of the Study:

• To investigate the potential of a cost-effective, non-toxic pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel.
• To enhance corrosion inhibition by functionalizing PMDI and optimizing its interaction with the zinc oxide layer on galvanized steel.
• To provide a microscopic understanding of the interaction mechanism between functionalized inhibitors and the zinc oxide surface.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to study the corrosion inhibition properties of PMDI derivatives.
• PMDI was functionalized with methyl/diamine groups to create three inhibitors: inh1, inh2, and inh3.
• Analysis included orbital energies, electronegativity, dipole moment, global hardness, electron transfer, charge density, and density of states.

Main Results:

• The functionalized inhibitor inh3 demonstrated superior corrosion inhibition performance compared to inh1 and inh2.
• Inh3 exhibited a significantly stronger interaction energy (∼182.38 kJ/mol) with the ZnO(101̅0) surface than inh2 (∼122.56 kJ/mol) and inh1 (∼119.66 kJ/mol).
• Specific N-Zn and H-O bonds formed between inh3 and the ZnO surface, absent in inh1 and inh2, due to favorable charge distribution and available electronic states.

Conclusions:

• The functionalized pyromellitic diimide derivative, inh3, is a highly effective corrosion inhibitor for galvanized steel.
• The enhanced performance of inh3 is attributed to strong interactions with the ZnO surface, facilitated by specific chemical bonding.
• This study provides valuable microscopic insights for designing advanced, low-cost, and efficient corrosion inhibitors for steel protection.