Enhanced anticorrosion performance of Antipyrine Derivatives on Mild Steel in an Acidic Environment: An Experimental and Theoretical Analysis

Abstract

Corrosion of mild steel poses significant economic and industrial concerns in various industrial applications. The recent study focuses on the investigation of corrosion inhibition properties of newly synthesized adamantyl amide derivatives of 4aminoantipyrine (M1, M2, and M3) on mild steel in 1.0 M HCl solution through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) techniques, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), adsorption isotherm model, temperature effect, thermodynamic parameters and computational studies. The as-synthesized amides (M1, M2, and M3) were characterized by proton ( 1 H-NMR), carbon-13 ( 13 C-NMR), and correlated nuclear magnetic resonance spectroscopy (COSY), heteronuclear single quantum coherence spectroscopy (HSQC), high resolution mass spectrometry (HRMS), and fourier transformed infrared spectroscopy (FTIR). The M1 show exceptionally high corrosion inhibition efficiency (IE%) of 97.89 ± 1.9 compared to M2 84.88 ± 1.7 and M3 95.02 ± 1.9 after 5 h immersion time. The experimental data shows the IE% increases by rising of concentration of inhibitors and immersion time while I.E% decreases by increasing the temperature during weight loss experiments. The M1 exhibits the activation energy (Ea) of 44.20 kJ/mol, enthalpy change (∆H) of 202.3 J/mol and entropy change (∆S) of -197.1 J/mol at 1.0 mM while the Gibb's free energy change (∆G) become less positive by rising the temperature, helps to deduce the mechanism of adsorption. In PDP measurements, the M1, M2 and M3 shows promising anticorrosion potential with IE% values 98.92, 98.22 and 94.76 respectively at 0.5 mM. The double-layer capacitance (Cdl) values during EIS experiments decreases by increase the concentration of inhibitors reveals their high anticorrosion properties. Furthermore, DFT studies were used to determine the inhibition mechanism.The lower energy gap of M1 compared to M2 and M3 indicates better electron donation to the mild steel. The work highlights the impact of steric hindrance on the anticorrosion properties of organic molecules.