Theoretical and experimental evaluation on adsorption and corrosion mitigation mechanism of isoxazoles for N80 steel in HCl solution

Ongoing advancements in both hardware and software have paved the way for the cost-effective utilization of computational measurements such as density functional theory (DFT), Fukui indices and Monte Carlo simulations (MCS) in corrosion inhibition study. In the present investigation, the anti-corrosion behavior of isoxazoles, namely, 5-(furan-2-yl)-3-(4-methoxyphenyl) isoxazole (FMPI) and 2-methoxy-6-(3-(4-methoxyphenyl)isoxazole-5-yl)phenol (MMIP) has been studied for N80 steel (NS) in 15% hydrochloric acid solution using density functional theory (DFT), Fukui indices, Monte Carlo simulations (MCS), weight loss measurement, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) methods. The compounds FMPI and MMIP exhibited corrosion prevention efficacy of 96.88 and 94.31%, respectively, at 400 ppm concentration and 303 K temperature by adsorbing on NS surface through mixed adsorption by obeying Langmuir isotherm. PDP studies suggested that both compounds (FMPI and MMIP) act as mixed corrosion inhibitors by efficiently inhibiting both anodic dissolution of NS and cathodic evolution of hydrogen processes. EIS studies showed that charge transfer resistance increases and double layer capacitance decreases on increasing the concentration of both inhibitors due to their adsorption on NS surface. The results of surface analysis performed by FE-SEM, AFM and XPS suggested the development of inhibitor layer at the NS surface to prevent its corrosion. DFT calculations suggested good reactivity for both inhibitors and confirmed their efficient corrosion inhibition activity. The MCS studies confirmed strong molecular adsorption of both inhibitors on the Fe(110) surface, thus exhibited effective NS surface protection. The computational outcomes about corrosion inhibition behavior of both inhibitors were in good agreement with the experimental observations.