Electrochemical Impedance Spectroscopy (EIS) and Study of Iron Corrosion Inhibition by Turmeric Roots Extract (TRE) in Hydrochloric Acid Solution

TURMERIC Root extract (TRE) was tested as corrosion inhibitor for iron in 0.5 M HCl, using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Scanning electron microscope (SEM), and energy dispersive X-rays (EDX) analysis. The inhibition efficiency raised as in time of immersion rises, but decreases with temperature rise. The Nyquist plots showed that, the charge transfer resistance (Rct) increase, and the double layer capacitance (C-dl) decreases with time of immersion increase. Tafel results exhibit that both corrosion current and with corrosion speed are reduced with time of immersion. All impedance spectra of EIS tests exhibit one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. IF (%) increases with the concentration of the inhibitor reaching its maximum value, 88. 90%, at 8g/100ml. Thermodynamics parameters: Ea, Delta H*, Delta S* were estimated, and mechanism of corrosion and inhibition was discussed. The adsorption of (TRE) followed Langmuir adsorption isotherm.