Performance of newly synthesized pyrimidine derivative as corrosion inhibitor: experimental and quantum chemical investigation

In this investigation, an alternative Schiff base with a pyrimidine ring was produced through the reaction of (1-amino-4-phenyl-2-thioxo-1,2-dihydropyrimidin-5-yl)(phe­nyl)me­tha­no­ne (1) with thiophene-2-carboxaldehyde. Structural verification of the resulting com­po­und, designated (E)-phenyl (4-phenyl-1-(thiophen-2-ylmethyleneamino)-2-thioxo-1,2-di­hy­dro­py­rimidin-5-yl)methanone, (PPTT), was accomplished by employing a number of spec­troscopic methods, including 13C-NMR, 1H-NMR, and FTIR. Open-circuit potential, potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy were among the electrochemical methods used to evaluate the efficacy of PPTT as a corrosion inhibitor. After one hour of immersion, experimental data showed that PPTT functioned as a mixed-type corrosion inhibitor, attaining up to 83.8 % inhibition for 2 mM PPTT in 1 M HCl solution. Under these conditions, the corrosion current density dropped from 123.2 to 31.4 μA cm-2. Surface adsorption of PPTT on mild steel in 1 M HCl followed the Langmuir adsorption isotherm, consistent with a negative Gibbs free energy value, indicating both chemisorption and physisorption. In addition, multiple quantum che­mical parameters (electronegativity, EHOMO, ELUMO, chemical hardness, chemical softness) were calculated using Gaussian 09 to further elucidate the experimental observations.