Experimental and theoretical assessments of an innovative star-shaped polyamine surfactant designed for X-65 steel corrosion mitigation in acidic environment

Abstract

Abstract The extant study introduces newly fabricated star-shaped polyamine surfactant ( PAS ) as a highly effective corrosion inhibitor for carbon steel ( X-65 ) in 1.0 M HCl environment. The PAS was synthesized by reaction of dodecyl amine with maleic anhydride via ring-opening reaction forming a monomaleate amide that was esterified with triethanolamine to yield a star-shaped structure, followed by Michael addition reaction using diethylenetriamine. The chemical structures of PAS were confirmed by FT-IR and 1 HNMR. Surface tension measurements were employed to quantify the key surface properties of PAS . The inhibition performance was comprehensively evaluated through electrochemical techniques, surface characterization, and theoretical computations. Electrochemical impedance spectroscopy ( EIS ) revealed an exceptional inhibition efficiency of ~ 96% at an optimal concentration of 1000 µM, with the charge transfer resistance increasing significantly to 348.56 Ω cm 2 . Potentiodynamic polarization ( PDP ) measurements demonstrated that PAS operated as a mixed-type inhibitor through suppressing both anodic and cathodic reactions. The inhibition mechanism was governed by the spontaneous adsorption of PAS molecules onto the X-65 surface, which follows the Langmuir adsorption isotherm suggesting a combination of physical and chemical adsorption. Surface morphology analysis utilizing scanning electron microscopy ( SEM ), energy-dispersive X-ray spectroscopy ( EDX ), and atomic force microscopy ( AFM ) provided direct evidence of the protective adsorbed film of PAS . Furthermore, theoretical assessments using density functional theory ( DFT ), and Monte Carlo simulations ( MCs ) successfully predicted the PAS active sites and its strong adsorption affinity onto the Fe surface, corroborating the experimental findings.