Polarization, EIS and EN Studies to Evaluate the Inhibition Effect of Vanillin as Environment-friendly Inhibitor on Carbon Steel in Hydrochloric Acid Solution

Vanillin is an interesting corrosion inhibitor because of its safe use and high solubility in water. The effect of vanillin on the corrosion inhibition of carbon steel in 1.0 M hydrochloric acid solution has been studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques. The effect of temperature on the rate of corrosion in the absence and presence of vanillin was also studied. Some thermodynamic parameters were computed from the effect of temperature on corrosion and inhibition processes. Adsorption of vanillin was found to obey Langmuir adsorption isotherm. Furthermore, in this paper the electrochemical noise (EN) technique under open circuit conditions was employed for the quantitative evaluation of corrosion inhibition. This was done by using the standard deviation of partial signal (SDPS) for calculation of the amount of noise charges at the particular timescale range, thereby obtaining the inhibition efficiency (IE) of an inhibitor. These IE values show a reasonable agreement with those obtained from potentiodynamic polarization and EIS measurements.