Bio-inspired corrosion control: Experimental and theoretical study of Cola lepidota on steel in acid

Abstract

This study presents a protective strategy for the corrosion protection of carbon steel in acidic environment utilizing Cola lepidota seeds extract, an agricultural waste product. The study employed both electrochemical (Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP)), and gasometric methods. The adsorption of the extract onto steel surface was thoroughly investigated using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), while the adsorption properties of its phytocompounds were investigated using theoretical approaches. Cola lepidota functioned as an effective mixed-type anticorrosion material, with its efficiency significantly determined by concentration, temperature, and duration of exposure. The efficiency of the extract improved with concentration, achieving optimal values of 98.5 % (EIS) and 91.7 % (gasometry) at 2.0 g/L. However, it decreased with elevating temperatures and prolonged exposure. The adsorption of the extract and its anticorrosive properties on the steel surface was subsequently confirmed by SEM and FTIR analyses. Thermodynamic data indicated that while some inhibitor molecules underwent chemical adsorption at elevated concentrations, the predominant mechanism was physisorption with exothermic characteristics. Furthermore, quantum chemical descriptors provided insights into the detailed understanding of the stability and reactivity of some identified phytocompounds in the extract, while molecular dynamics simulations shed light on the specific adsorption behavior and orientation of the phytocompounds, thereby enhancing our comprehension of the protective mechanism of Cola lepidota seed extract. This research demonstrates a sustainable "waste-to-wealth" approach by transforming an underutilized waste product into a highly effective and sustainable corrosion inhibitor, advancing the drive for green solutions to corrosion mitigation.