Effect of green and sustainable extracted fucoidan polysaccharide as a corrosion inhibitor in 3.5% NaCl.

This study examined the corrosion inhibition of 304 stainless steel (304 SS) with fucoidan in 3.5% NaCl solution using both chemical and electrochemical methods, including mass loss as a chemical method and electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) as an electrochemical method. The fucoidan compound was verified and characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy, and morphology characteristics. The PP curves indicate that fucoidan was an effective corrosion inhibitor for 304 SS in 3.5% NaCl solutions, which indicates that the compound is a mixed-type inhibitor. It was shown that by adding the fucoidan inhibitor, the corrosion potential (Ecorr) and Tafel lines were slightly shifted. With the compound added, the value of the double-layer capacitance was reduced. In the case of 200 ppm, it reached maximum efficiencies of 81.7%. After studying its adsorption behavior on 304 SS, the Langmuir isotherm and chemical adsorption were concluded. It was necessary to compare the theoretical computations with the experimental findings using both density functional theory (DFT) and Monte Carlo simulations (MC). [ABSTRACT FROM AUTHOR]