Abstract
Different solvents were used to extract Griffonia simplicifolia and tested corrosion inhibitors for as X80 steel in 1 M HCl solution. The corrosion tests were conducted by thermo-gravimetric analyses (TGA), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) while the surface morphologies were checked by scanning electron microscopy (SEM). The essence was to investigate the effects of the solvents on the yield, phytochemical profile, corrosion inhibition properties and thermal stability of the extracts. The highest yields of 63.24 g kg -1 and 51.63 g kg -1 were obtained with seeds (SEGS) and leaves (LEGS) extracts respectively in ethanol-water (1:1) system. Acetone extract showed presence of all the tested phytochemicals namely alkaloids, tannins, saponins, glycosides, steroids and terpenoids. The highest inhibition efficiencies of 95.86 % (SEGS) and 82.14 % (LEGS) were obtained with acetone extracts. Acetone extract was also most thermally stable being 66.4 % (SEGS) and 50.05 % (LEGS) efficient at 90 °C, followed by ethanol extract while methanol extract was least stable and least efficient. Inhibitors act as mixed type and their addition increased charge transfer resistance and decreased corrosion current density with respect to the free acid solution. Micrographs of the steel surface in some systems show evidence of slight surface protection by the inhibitors. It has been inferred from this study that both acetone and ethanol are better solvents for extraction of Griffonia simplicifolia based corrosion inhibitors.
Highlights
The choice of Griffonia simplicifolia is due to the broad alkaloid composition which has been reported about the plant, especially the presence of 5hydroxytryptophan.[15]
Alkaloids are detected in extracts of all the solvents studied while flavonoids were not detected in any. These result are in partial agreement with those reported for seeds of Griffonia simplicifolia in Ghana.[17]
It was earlier observed that acetone extract contained all the phytochemicals tested, which may be responsible for the high inhibition efficiency obtained
Summary
Different solvents were used to extract Griffonia simplicifolia and tested corrosion inhibitors for as X80 steel in 1 M HCl solution. The essence was to investigate the effects of the solvents on the yield, phytochemical profile, corrosion inhibition properties and thermal stability of the extracts. The highest yields of 63.24 g kg-1 and 51.63 g kg-1 were obtained with seeds (SEGS) and leaves (LEGS) extracts respectively in ethanol-water (1:1) system. The highest inhibition efficiencies of 95.86 % (SEGS) and 82.14 % (LEGS) were obtained with acetone extracts. Micrographs of the steel surface in some systems show evidence of slight surface protection by the inhibitors. It has been inferred from this study that both acetone and ethanol are better solvents for extraction of Griffonia simplicifolia based corrosion inhibitors.
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