Abstract:
The effectiveness of three plant extracts namely Glycine max leaves (GMLE), Cuscuta reflexa roxb. (CRRE) and
Spirogyra algae (SGAE) has been evaluated as green corrosion inhibitors for mild steel corrosion in acidic solution of 1 M HCl using chemical, electrochemical, surface and density functional theory (DFT) methods. The
gravimetric and electrochemical results showed that the trend of their effectiveness towards mild steel acidic
corrosion inhibition follows the order: GMLE > CRRE > SGAE. Polarization study suggested that tested plant
extracts acted as mixed type inhibitors with slight anodic dominance. The GMLE, CRRE and SGAE extracts
showed maximum inhibition efficiencies of 73.60%, 81.92% and 94.05%, respectively at 2 g L−1 concentration.
Results of gravimetric measurements showed that effectiveness of the plant extracts enhances on enhancing their
concentrations. Gravimetric measurements carried out at different temperature showed that adsorption of the
plant extracts mainly involve physisorption mechanism. Investigated extracts behaved as interface inhibitors and
their adsorption mechanism obeyed the Langmuir adsorption isotherm. Surface morphology and elemental
composition was determined to support the adsorption inhibitive mechanism. Scanning electron microscope
(SEM) analyses carried out in the association with electron dispersive X-ray spectroscopy (EDS) further supported the adsorption inhibitive mechanism. Density Functional Theory (DFT) study was carried out on major
phytochemicals present in the extract in order to support the experimental results and explain the adsorption
behaviour of phytochemicals (extracts).
