Curcuma Zedoaria Extract as a Novel Corrosion Inhibitor for Mild Steel in 0.5 M H2SO4

In this study, curcuma zedoaria extract was investigated as a mild steel (MS) corrosion inhibitor in 0.5 M H2SO4 solution by conventional methods of weight loss (WL), electrochemical impedance spectroscopy (EIS) and polarization at 25 °C. The highest percentage of inhibition was obtained for the concentration of 0.5 g/l of curcuma zedoaria extract. The results of polarization method showed that curcuma zedoaria extract acts as a mixed inhibitor. Examination of MS immersion time by weight loss method showed that with increasing immersion time, the inhibitory effect decreases in low concentrations of curcuma zedoaria extract but in higher concentrations of curcuma zedoaria extract (concentration 1.0 g/L), the inhibitory effect remains almost constant over time. The effect of temperature on the performance of curcuma zedoaria extract by electrochemical polarization method in the temperature range of 35-65 °C shows a decrease in inhibition percentage with increasing temperature. Adsorption of curcuma zedoaria extract molecules on the surface of MS at all studied temperatures follows the Langmuir adsorption isotherm. Using the results of kinetic and thermodynamic calculations, the adsorption of molecules of curcuma zedoaria extract on the surface of MS physical adsorption type was observed.