Quantum chemical and mathematical statistical calculations of phenyltetrazole derivatives as corrosion inhibitors for mild steel in acidic solution: A theoretical approach

The use of organic compounds to prevent the corrosion of mild steel has become widespread in recent years. Among the countless chemical compounds used as possible inhibitors, phenyltrazole derivatives stand out as inexpensive and effective molecules in various electrolytes. This research examines the computational charac-teristics of selected phenyltrazole compounds investigated as inhibitors of mild steel deterioration in HCl me-dium using a quantum chemical approach (Density Functional Theory) and mathematical calculations. The inhibitory effectiveness of three phenyltrazole compounds: 5-(4-chlorophenyl)-1H-tetrazole (CL-PT), 5-(4-methoxyphenyl)-1H-tetrazole (MO-PT), and 5-phenyl-1H-tetrazole (PT) was investigated. The quantum chemical parameters, such as the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied mo-lecular orbital (ELUMO), the energy gap (AE), the dipole moment (d), chemical hardness (q), softness (a), elec-tronegativity (chi), back donation (Aback donation), and global electrophilicity (o) were evaluated. The results of the quantum chemical calculations revealed that the three compounds have a good anti-corrosion capacity. The order of inhibition efficiency was CL-PT > MO-PT > PT. In addition, cross-checking the data with experimental analysis confirms the theoretical calculations. In mathematical calculations, four mathematical models are suggested. First, second, third, and n-order models are tested. The third-order model was the best one with a high correlation coefficient.