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 inwater. The effect of vanillin on the corrosion inhibition of carbon steel in 1.0 Mhydrochloric 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 vanillinwas also studied. Some thermodynamic parameters were computed from the effect oftemperature on corrosion and inhibition processes. Adsorption of vanillin was found to obeyLangmuir adsorption isotherm. Furthermore, in this paper the electrochemical noise (EN)technique under open circuit conditions was employed for the quantitative evaluation ofcorrosion 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, therebyobtaining the inhibition efficiency (IE) of an inhibitor. These IE values show a reasonableagreement with those obtained from potentiodynamic polarization and EIS measurements.