Pectin extracted from Vicia faba waste as a corrosion inhibitor for mild steel

Polysaccharides derived from renewable resources are gaining attention as sustainable and eco-friendly corrosion inhibitors. This study explores the extraction and characterization of polysaccharides from broad bean pods (Vicia faba), an agricultural by-product, and evaluates their effectiveness as corrosion inhibitors for mild steel. Structural characterization of the polysaccharide extracted from broad bean (PBB) was performed using Fourier transform infrared spectroscopy, Gas chromatography-mass spectrometry, and Size Exclusion Chromatography. The results indicated that the polysaccharide was a rhamnogalacturonan II (RG-II) with high molecular weight. The corrosion of mild steel was studied in the presence of PBB in 0.1 M HCl solutions. Maximum inhibition efficiency of 87.07 % was achieved at a concentration of 0.7 g/L of PBB. Electrochemical techniques, including potentiodynamic polarization and electrochemical impedance spectroscopy, revealed that PBB effectively inhibited both cathodic and anodic corrosion reactions. The adsorption of PBB on the steel surface followed the Langmuir adsorption isotherm. Infrared spectroscopy and scanning electron microscopy confirmed the formation of a protective film on the metal surface. This study underscores the potential of polysaccharides as effective, non-toxic, and environmentally friendly alternatives to traditional synthetic corrosion inhibitors.