Anticorrosion and rheological properties of Calyptocarpus vialis extract as a green coating for mild steel in 2MH2SO4

Abstract

This study assesses the rheological properties and corrosion inhibition efficacy of Calyptocarpus vialis (CV) extract, a wild plant in Asteraceae family. Shear and dynamic rheology studies show that CV extract has shear-thinning behaviour, with viscosity changes occurring at higher shear rates, most likely owing to aggregate formation. These aggregates may develop due to certain solvent characteristics and a jamming tendency is due to the presence of extract phytochemicals. Dynamic rheology confirms its viscoelastic nature. Corrosion inhibition effectiveness was investigated using Mild Steel (MS) in 2 M H2SO4, resulting in an 82.69 % inhibition with an extract concentration of 1 g/L. Adsorption isotherm indicates phytochemical adsorption on MS surface. Contact angles of polished MS (87.30°), with extract (80.10°), and without extract (51.25°) show decrease in wetting and increase in hydrophobicity which indicates that a thin protective layer is formed at MS surface. FE-SEM (Field Emission Scanning Electron Microscopy) images reveal that the CV extract forms a protective barrier on the MS surface, significantly reducing corrosion as compared to the unprotected surface exposed to the mild acid solution. Theoretical calculations, including Density Functional Theory (DFT) simulations, Monte Carlo (MC), and Molecular Dynamics (MD) simulations, support the experimental findings, elucidating phytochemicals adsorption on the MS surface. Further research is required to examine the scalability of CV extracts for industrial applications, as well as their long-term stability and efficacy in various corrosive conditions.