Detailed experimental and computational explorations of pyran derivatives as corrosion inhibitors for mild steel in 1.0 M HCl: Electrochemical/surface studies, DFT modeling, and MC simulation

Abstract

The present paper examines the adsorption of two novel heterocyclic compounds of the pyran derivatives, namely 2-amino-5-oxo-4-(p-tolyl)-4H,5H-pyrano [3,2-c]chromene-3-carbonitrile (PY-CH3) et 2-amino-5-oxo-4-phenyl-4H,5H-pyrano [3,2-c]chromene-3-carbonitrile (PY-H)against corrosion of mild steel in molar HCl medium. The experimental investigation was carried out using several techniques including Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP). The inhibition efficiencies of PY-CH3 and PY-H followed the order: 80.0% (PY-CH3) < 90.0% (PY-H). The adsorption process of PY-CH3 and PY-H on the mild steel surface follows Langmuir adsorption model. Surface characterization analysis using Scanning Electron Microscopy (SEM) coupled with Energy dispersive X-ray analysis (EDS), Atomic Force Microscopy (AFM), X-ray diffraction analysis (XRD), and Infrared Spectroscopy (FT-IR) supported the formation of a barrier layer that covers the mild steel surface. WL measurements were also tested using inductively coupled spectroscopy (ICP) and UV-Vis spectrometry (UV-Vis). The interaction mechanism of PYCH3 and PY-H with mild steel surface and their mode of adsorption were studied using DFT and Monte Carlo (MC) simulations, respectively.