Effect of three substituted dihydroimidazole corrosion inhibitors on carbon steel surfaces: experimental and theoretical studies of inhibition and adsorption performance

Abstract

Corrosion resistance and adsorption attributes of three synthesized dihydroimidazoles, namely (4R,5S)-2,4,5-tris(3,4,5-trimethoxyphenyl)-4,5-dihydro-1H-imidazole (TMPI), (4R,5S)-2,4,5-tris(4-(methylthio)phenyl)-4,5-dihydro-1H-imidazole (MSPI), and (4S,5R)-2,4,5-tri(thiophen-2-yl)-4,5-dihydro-1H-imidazole (TTPI), were scrutinized for carbon steel in 1 M HCl employing a combination of analytical techniques, including electrochemical and instrumental, alongside quantum computational methods. Electrochemical experiments revealed that the effectiveness of corrosion inhibition is influenced by the substituted dihydroimidazoles' concentration and structure. The inhibition efficiency reached remarkable levels: 98.53% for TTPI, 98.59% for TMPI, and 99.12% for MSPI at 0.001 M. The Tafel polarization method indicated that these synthesized dihydroimidazoles function as mixed-type inhibitors. The adsorption process of synthesized dihydroimidazoles adheres to the Langmuir adsorption isotherm. Various analytical techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), contact angle, atomic force microscopy (AFM), and X-ray diffraction analysis (XRD), confirmed that substituted dihydroimidazoles form a protective layer that inhibits carbon steel dissolution. Furthermore, molecular dynamics (MD) was utilized to investigate the adsorption behavior of substituted dihydroimidazoles on the Fe (110) surface, determining the entanglement order of their interaction. The radial distribution function (RDF) revealed that corrosion inhibitors employ a complex adsorption mechanism on metal surfaces, primarily driven by chemical processes and supplemented by physical adsorption.