Quantum chemical study on the inhibition efficiencies of some sym-triazines as inhibitors for mild steel in acidic medium

•Quantum chemical calculations were performed on five sym-triazine inhibitors.•NBO charges and PA were used to determine the atom at protonation process.•Inhibition efficiency follows the order: HPAT > HPMeT > HPTT > HTT > HPNT.•It was found a correlation of calculated parameters with the inhibition efficiencies.

Quantum chemical calculations using density functional theory (DFT) at the B3LYP/6-31++G(d,p) basis set level were performed on five sym-triazines used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their percentage inhibition efficiencies. The results of the calculations and experimental IE% were subjected to correlation analysis and indicate that their inhibition effect are closely related to EHOMO, ELUMO, energy gap, hardness, softness, electronegativity and the fraction of electrons transferred were calculated. The theoretically obtained results were found to be consistent with the experimental data reported.