Development of a high-performance anticorrosive system based on 1,2,4-triazine derivative: Experimental and theoretical investigations

1,2,4-triazine heterocycles show an extensive capacity to protect metal surfaces from corrosion. Herein, we report the synthesis, spectroscopic characterization, and anti-corrosion inhibition efficiency of a novel 5,6-diphenyl-3-(prop-2-yn-1-ylthio)-5,6-dihydro-1,2,4-triazine (DPDT). The anticorrosion performance of DPDT was evaluated for mild steel in 1.0 M HCl using electrochemical, surface analysis, and theoretical techniques. Potentiodynamic polarization results revealed that DPDT acts as a cathodic-type inhibitor, achieving a maximum inhibition efficiency of 96.1% at a concentration of 10⁻³ M, with corrosion current density reduced from 810 to 31 µA·cm⁻ ². EIS analysis confirmed the formation of a protective layer, with the polarization resistance (R_p ) increasing from 33.20 to 540.90 Ω·cm² and the double-layer capacitance decreasing accordingly. The adsorption of DPDT obeys the Langmuir isotherm model, with a calculated ΔG⁰_ads of −19.98 kJ·mol⁻ ¹, indicating a physisorption mechanism. DFT calculations and MD simulations reveal that the protonated form DPDTN1H⁺ is the favorable form for adsorption on the metal surface with an adsorption energy of −498.9 kcal/mol. SEM-EDX analysis confirmed surface protection and the presence of DPDT on the steel surface. These results demonstrate that DPDT is a highly efficient, stable, and surface-active corrosion inhibitor, offering promising potential for industrial applications.