Experimental methods have been employed to elucidate the corrosion inhibition mechanism, but they are often expensive and time-consuming, necessitating the search for more alternatives. The development of computer hardware and software engineering has allowed the effective use of theoretical modeling tools that successfully correlate the inhibition efficiency of the inhibitors with their molecular structure and properties. In this study, computational methods were used to further explain the mode and mechanism of the thiadiazoles inhibition on Fe surface whose studies were reported in the literature as Thiadiazoles-A potential class of heterocyclic inhibitors for prevention of mild steel corrosion in hydrochloric acid solution. Parameters including quantum chemical through DFT and molecular dynamic simulations of studied molecules on Fe surfaces were performed. Results obtained by calculating these thiadiazoles' adsorption or binding energies were in good agreement with the experimentally reported results elsewhere. Concerning the calculated adsorption or binding energies, their relatively low values inferred that the compounds are weakly adsorbed onto the surface of Fe through Van der Waals forces and therefore obey the mechanism of physical adsorption. Fukui indices values revealed that the active sites were found to be located on the molecules heteroatoms (Sulphur and Nitrogen). It was also established that the reference molecule thiadiazole (TDA) was the least adsorbed when compared to the other four molecules of its derivatives. The order of the inhibition efficiency as determined is as follows: PAT > EAT > MAT > AT > TDA

Whenever metals and metal-based materials interact with their environment (chemically, biochemically, or electrochemically), surface loss occurs, a process termed as corrosion. Corrosion is one of the important challenges which leads to the reduction of product life. In recent years, due to the growing interest of the world in protecting the environment and the harmful effects of using chemicals on ecological balance, the traditional approach with respect to corrosion inhibitors has gradually changed. Azole compounds have received a lot of attention in the oil, gas, and petrochemical industries since their structures prevent corrosion in acidic and alkaline environments. Also, due to having elements such as nitrogen and sulfur in their structure, they have been used widely as anti-fungal and anti-bacterial materials in the pharmaceutical industry as well. In this study, azole organic compounds, the encapsulation methods, and the mechanism of action of these compounds on the corrosion behavior of metallic surfaces have been investigated.

Quantum chemical calculations and molecular dynamics simulation techniques were used to assess the corrosion inhibition potential of the compound qiunazoline (QZN) and two of its derivatives, 6-chloro-4-imino-3-phenyl-3,4-dihydro-1H qiunazoline-2-thione (QZT) and 6-chloro-4-imino-3-phenyl-3,4-dihydro-1H qiunazoline-2-one (QZO). The values of the quantum chemical parameters EHOMO, ELUMO, energy gap (∆E), the energy of back donation (∆Eb-d), dipole moment (μ), electronegativity (χ), global hardness (η), global electrophilicity index (ω), nucleophilicity (ε) and others were determined. The quantum chemical parameters calculated revealed that QZO is relatively more nucleophilic in nature and potentially a better inhibitor. The Fukui indices values discovered that the hetero atoms (N, O and S) of the studied compounds are responsible for their inhibitive characteristics. According to the calculated binding and adsorption energies obtained from the quenched molecular dynamic simulations, the relatively low values obtained of less than 100 kcal/mol results in the molecules being weakly adsorbed onto the surface of Al(1 1 0) through van der Waals forces and consequently obey the physical adsorption mechanism in the order: QZO>QZT> QZN. The examined molecules' varied bond lengths and angles before and after adsorption on the Al(1 1 0) surface demonstrate the nature of adsorption and the molecules' non-planarity on the surface of the metal. QZO and QZT have larger molecular sizes and additional hetero atoms (O and S), making them possibly more corrosion-inhibitive on Al(1 1 0) surfaces than QZN.