Enhanced carbon steel protection via sepiolite-lignin biocomposite: Multifactor design in chloride solution

초록

Industries are highly confronted with the corrosion of materials due to chemical reactions with their environment, which poses a major issue leading to significant material damage. In the present work, the corrosion resistance of sepiolite-lignin biocomposite (SP-L) for carbon steel (CS) in a 3 wt% NaCl solution was assessed by means of electrochemical impedance spectroscopy (EIS) measurements. The experimental study was planned by Response Surface Methodology (RSM) using Box-Behnken design (BBD)-based optimization to analyze the factors that influence the corrosion resistance. Under the optimized conditions of near-neutral pH (6.8), 100 mg inhibitor dose, and 24 h immersion time, the Box-Behnken design yielded a predicted corrosion resistance (Rp) of approximately 8755 S2 cm2 with a high coefficient of determination (96 %). Experimentally, Rp values reached up to 9350 S2 cm2, confirming strong agreement between model forecasts and observed data. Monte Carlo simulations further revealed highly negative adsorption energies of -493.942 kcal/mol (sepiolite-lignin) and -209.791 kcal/mol (iron-lignin), underscoring the spontaneous and robust surface adhesion responsible for enhanced carbon steel protection. Overall, these investigations proved that SP-L effectively inhibits corrosion of CS in a 3 wt% NaCl medium through adsorbing onto the CS surface and forming a protective layer.

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