Broad bean stalk extract as a novel eco-friendly corrosion inhibitor for cold rolled steel in HCl medium: Experimental and theoretical investigation

Abstract

The ultrasonic extraction technique was used in this work to prepare the agricultural waste of broad bean (Vicia faba) stalks extract (VFSE). By employing a range of experimental techniques and theoretical computations, the corrosion inhibition performance of VFSE on cold rolled steel (CRS) in 1.0 M HCl medium was examined. The results revealed that the maximum inhibition efficiency was 90.3 % at a VFSE dosage of 100 mg L⁻¹, and showed well inhibition stability at different temperatures within 48 h. VFSE also displayed mixed-type inhibitory characteristics and the polarization resistance increased by 8 times after adding VFSE. Increasing the concentration of VFSE resulted in higher charge transfer resistances (797.7 Ω cm²) in electrochemical impedance spectroscopy (EIS) measurements. Moreover, surface characterization confirmed the adsorption of VFSE on the CRS surface as a film. Time-of-flight secondary ion mass spectrometry technique provided stronger evidence for the adsorption of VFSE on the CRS surface. It was confirmed by liquid chromatograph-mass spectrometer and theoretical calculations that flavonoids, alkaloids and esters could be effectively adsorbed on the CRS surface, and the benzene rings, O/N heterocycles and -OH functional group contained in these components were the active sites. These active sites demonstrated strong chemisorption interactions with the CRS substrate, thereby corroborating the effective corrosion inhibition performance of VFSE from a theoretical perspective.