3-Phenylquinazolin-4(3H)-one via a renewable approach as an efficient corrosion inhibitor for mild steel in acid media

Abstract

3-phenylquinazolin-4(3H)-one (3pq) an organic aza-heterocyclic compound synthesised using a renewable biomass source, and the structure is subsequently confirmed using 1H NMR, 13C NMR and FT-IR spectroscopic techniques. The inhibition activity of 3pq was examined with a set of experiments like Weight loss measurements which provided a high inhibition efficiency (IE) of 90.0% and a low corrosion rate (CR) of 1.54 mm/y at 300 ppm. Electrochemical studies such as potentiodynamic polarization study confirmed the mixed inhibition activity of the inhibitor molecule with low corrosion current (icorr) value of 17.4 μA/cm2 in the presence of higher concentration of 3pq, and electrochemical impedance spectroscopy showed higher charge transfer resistance (Rct) value of 524.81 Ω cm2 and all these experiments have been used to examine 3pq′s inhibiting capability for MS in 1 N HCl solution. The examined compound's ability to prevent corrosion is less effective in higher temperature. 3pq followed the Langmuir adsorption isotherm, which showed higher linearity than the Freundlich and Temkin adsorption isotherm models. The surface morphology was examined using scanning electron microscopy (SEM), which showed a smoother surface corresponding to the formation of a protective film signifying effective adsorption of inhibitor on MS surface, atomic force microscopy (AFM) signifies lower surface roughness (19.62 nm) in inhibited MS when compared to the uninhibited MS (81.63 nm) and Contact angle measurement explains the formation of the hydrophobic layer of 3pq on the surface of the MS in which the contact angle rises from 48.5° (uninhibited MS) to 99.7° (inhibited MS). UV–Visible spectroscopy (UV–Vis.) was employed to explain the complex formation of the inhibitor at the MS surface. X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red Spectroscopy (FTIR) was employed to confirm the effective adsorption of inhibitors on the MS surface. Additionally, computational studies based on Density functional theory (DFT) was employed to study the ability of 3pq to get adsorbed on the MS surface and found that 3pq has a perfect affinity to get adsorbed on the MS.