The inhibitive effect of Thevetia peruviana on
the corrosion behavior of carbon steel in 1 M HCl was
studied using the weight loss method, polarization, AC
electrochemical impedance spectroscopy and electrochemical frequency modulation techniques. The inhibition
efficiency was found to depend on the concentration of the
extract and the temperature of the medium. Results showed
that this extract acts as a mixed-type inhibitor. The charge
transfer resistance increases but the double layer capacitance decreases by increasing the extract concentration. It
was found that the investigated extract acts via adsorption
on the carbon steel surface and obeys the Temkin adsorption isotherm. The effect of temperature on the corrosion
rate in the absence and presence of the extract was investigated, some activated, and the adsorption parameters
were calculated. The results of the electrochemical methods were in good agreement with the weight loss measurement results