Abstract
The inhibiting effect of nonionic surfactant of Tween-20 and 60 on the corrosion of mild steel in 0.5 M HCl was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The results show that inhibition efficiency increases with increasing the inhibitor concentration, while it decreases with increasing the temperature. The adsorption of Tweens on the mild steel surface obeys the Langmuir adsorption isotherm. The effect of temperature on the corrosion behavior of mild steel was also studied at four temperatures ranging from 25 to 55 degrees C the thermodynamic parameters were calculated and discussed. The values of free energy of adsorption for investigated Tweens were calculated. It was found the adsorption process is spontaneous and increases, in the same direction as inhibition efficiency. Polarization curves show that Tween-20 and 60 is mixed-type inhibitors but the cathode is more polarized than the anode. The results obtained from chemical and electrochemical techniques are in good agreement.