Vigna unguiculata Coat Extract as Green Corrosion Inhibitor for Steel Pipeline in HCl

Abstract

The inhibitive performance of aqueous Vigna unguiculata coat extract on the corrosion of pipeline steel in 0.5 M HCl solution was studied by electrochemical, Gravimetric and UV-Visible spectroscopy techniques at varying temperatures. The extract was characterized using Gas Chromatography-Mass Spectrometer, GC-MS analysis. The results revealed that increase in concentration of extract yielded an increased inhibition efficiency up to 86.7% at 303 K; but showed a reversed trend at elevated temperature. The potentiodynamic polarization data indicate that aqueous Vigna unguiculata is a mixed type inhibitor of steel pipeline corrosion in acidic environment, while the electrochemical impedance spectroscopy result showed the extract's activity was on the solution-metal interface. Also, adsorption of aqueous Vigna unguiculata coat molecules on steel pipeline followed Temkin isotherm. The GC-MS results showed presence of heavy hetro-molecules. While, the adsorption of extract film deposited on the steel surface was characterized using FT-IR. The thermodynamic data strongly suggests that the mode of adsorption involved both physisorption and chemisorption.