A study on the corrosion inhibition impact of newly synthesized quinazoline derivatives on mild steel in 1.0 M HCl: Experimental, surface morphological (SEM-EDS and FTIR) and computational analysis

Two new quinazoline derivatives were investigated in this research, namely 12-(4-methoxyphenyl) and 3,3-dimethyl-12-(4-nitrophenyl)-3,4,5,12-tetrahydrobenzo[4,5]imidazo[2, 1-b]quinazolin-1(2 H)-one (Q-NO₂). In 1 M hydrochloric acid (HCl), −3,3-dimethyl-3,4,5,12-tetrahydrobenzo[4,5]imidazo[2,1-b]quinazolin-1(2 H)-one (Q-OMe) proved to be an extremely effective corrosion inhibitor for mild steel. The maximum inhibition efficiencies of 94.7 % for Q-NO₂ and 96.7 % for Q-OMe were achieved when the performance of the inhibitors was evaluated using potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM) and electrochemical impedance spectroscopy (EIS). According to these findings, the Q-NO₂ and Q-OMe molecules have a remarkable ability to generate a dense, resistant protective film on the mild steel surface. This protective film acted as a barrier, effectively blocking the penetration of corrosive ions and their interaction with the mild steel substrate. The adsorption characteristics of these inhibitors on the mild steel surface conform to the Langmuir adsorption isotherm. PDP experiments show that Q-NO₂ and Q-OMe act as mixed-type inhibitors for mild steel in 1.0 M HCl. Surface characterization by energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) determined that a protective layer had formed on the steel surface, preventing corrosion. The experimental results were corroborated by theoretical insights from density functional theory (DFT), which further clarified the molecular adsorption processes. This work highlights the potential of Q-NO₂ and Q-OMe as effective inhibitors to protect mild steel in acidic situation.