Protection of mild steel corrosion by three new quinazoline derivatives: experimental and DFT studies

The corrosion inhibition ability of three newly synthesized quinazoline derivatives namely, 2-chloro-N-(1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinazoline-3-carbonothioyl) propanamide (Q1), 2-methoxy-N-(1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinazoline-3-carbonothioyl) acetamide (Q2) and N-(1-methyl-2,4-dioxo-1,2,3,4-tetrahydroquinazoline-3-carbonothioyl) propionamide (Q3) on the mild steel (MS) in 0.5 M HCl medium have been examined by mass loss and electrochemical parameters. The obtained results of all the quinazoline derivatives exhibit excellent corrosion inhibition for MS and exhibited the maximum inhibition efficiencies (η %) of 95.50% (Q1), 91.33% (Q2) and 86.71 (Q3) at optimum concentrations. From electrochemical impedance spectroscopy (EIS) result, it is proved that, corrosion inhibition was achieved due to adsorption of quinozoline derivatives at the metal/electrolyte interface, on the other hand the studied derivatives fall under a category of mixed inhibitor as suggested by polarization results. The quinazoline derivatives adsorption on MS has been compiled well with Langmuir isotherm model. Scanning electron microscopy (SEM) was used to analyse the protective layer of inhibitors formed on MS surface. The efficiency of corrosion inhibition from mass loss and electrochemical measurements were in good agreement with each other. The correlation of molecular structures and inhibition efficiencies of three quinazoline derivatives was studied by using density function theory (DFT) method.