Effect of alkyl chain length on the corrosion inhibition performance of 2-thioxo-2,3-dihydroquinazolin-4(1H)-one derivatives for carbon steel in HCl solution

This article investigates two quinazoline derivatives for reducing carbon steel corrosion in acidic media, commonly encountered in various chemical processes, which contribute significantly to corrosion. The structurally simple and easily synthesized compounds, 3-methyl-2-thioxo-2,3-dihydroquinazolin-4(1H)-one (Q-C1) and 3-butyl-2-thioxo-2,3-dihydroquinazolin-4 (1H)-one (Q-C4), were evaluated as corrosion inhibitors for carbon steel in 1.0 M HCl solution using chemical, electrochemical, surface analysis, and quantum computational methods, with particular attention to the effect of alkyl chain length on the inhibition efficiency. The inhibitory efficiency reached 88.91% for Q-C4 at 4.0 × 10^-5, achieved during weight-loss testing on the carbon steel surface in 1.0 M HCl at 298 K. The temperature impact (ranging from 298 to 318 K) on the corrosion inhibition was investigated, revealing that with an increase in temperature, the inhibition efficiency diminishes. The kinetic and thermodynamic parameters were determined and analyzed to express the adsorption behavior of the studied inhibitors. The adsorption of the compounds on the carbon steel surface conforms to the Langmuir adsorption isotherm. The electrochemical measurements were conducted through the electrochemical impedance (EIS) and potentiodynamic polarization (PP) techniques, which confirm that the studied compounds were categorized as mixed-type inhibitors. EIS data reveal that charge-transfer resistance increases from 31.3 Ω cm² in the uninhibited solution to 261.61 Ω cm² in the inhibited solution of Q-C4. The surface of carbon steel was examined using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FT-IR), demonstrating the formation of a protective layer on the CS surface, mitigating the corrosion. Finally, the adsorption affinity of these compounds on the carbon steel surface was theoretically examined utilizing quantum calculations. The outcomes of the theoretical study in quantum chemistry were corroborated by data from chemical and electrochemical methods.