Adsorption of dithiazolidine compounds on Fe(110) surface and potential for corrosion inhibition: DFT calculations and adsorption locator/Monte Carlo adsorption simulations

Résumé

Many corrosion inhibitors act through an adsorption mechanism by forming a stable film that protects the surface from an aggressive environment. The adsorption behaviour of two dithiazolidine derivatives, namely, 3,5-diphenyl-imino-1,2,4-dithiazolidine (DPID) and 3-phenyl-imino-5-chlorophenylimino-1,2,4-dithiazolidine (PCID), on the Fe(110) surface was investigated via density functional theory (DFT) calculations and adsorption locator/Monte Carlo adsorption simulations. Quantum study results reveal that PCID exhibits higher HOMO energy, higher tendency to accept electrons, and greater molecular softness than DPID, though with a smaller HOMO--LUMO energy gap (Delta)E = 0.10355 Ha. Fukui function and Mulliken charge analyses led to the identification of sulphur atoms as the most active adsorption centres in both inhibitors. Adsorption locator/Monte Carlo adsorption simulations confirm that both compounds are strongly adsorbed on the Fe(110) surface in a parallel orientation. DPID and PCID afforded adsorption energies of -137.419 kcal mol-1 and -147.611 kcal mol-1, respectively, whereas the rigid adsorption energy of PCID reached -149.555 kcal mol-1, a demonstration of stronger surface binding. These highly negative adsorption energies suggest predominantly very strong inhibitor-surface interactions, and that both compounds have theoretical potential as corrosion inhibitors for Fe-based surfaces. However, the adsorption strength and predicted inhibition potential of PCID would be greater compared with DPID, which provides theoretical guidance for rational design and prioritization of dithiazolidine-based corrosion inhibitors for future experimental evaluation.

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