Evaluation of Shazab extract as eco-friendly green corrosion inhibitor for 420 stainless steel in hydrochloric acid

The effect of dried Shazab leaf extract (DSLE) as a green, eco-friendly corrosion inhibitor for 420 stainless steel (420 SS) in 0.5 M HCl was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic Tafel polarisation (PTP). Four types of isotherm models were applied to calculate the equilibrium adsorption constant (K-ads), and based on the value of the correlation coefficient (R-2), the Langmuir isotherm was found to be the best in this study. Moreover, based on the different thermodynamic parameters such as G(ads), H-ads, and Ea, the adsorption of DSLE on 420 SS was considered to be a physisorption process, and the adsorption was proved using FTIR and UV-vis spectroscopy. The degree of pitting that appeared on the metal surface was investigated in different concentrations of HCl and examined using microscopic photographs. Finally, the inhibition mechanism was studied.