Electrochemical Inhibitory Effects of Non-edible Vegetable Oils on Low-Alloyed Low Carbon Steel in H2SO4

Abstract

Corrosion inhibition mechanisms of Rubber, Neem and Jatropha seeds oils on low-alloyed low-carbon steel in 0.5 M·H2SO4 environment have been investigated herein. Potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron spectroscopy techniques were employed for the experimental process. The results obtained showed that inhibition efficiencies for Rubber, Neem and Jatropha seeds oils reached values of 99.957, 99.275 and 99.998%, respectively. The most shifts in corrosion potentials were > 85 and < 85 in positive directions for Rubber and Neem seeds oils, respectively, while Gibbs free energy of adsorption had values − 29.29 and − 15.06 and − 11.90 kJ/mol for Rubber, Neem and Jatropha seeds oils, respectively. Addition of oil inhibitors initiated formation of protective oxide films on substrate which contributed to increased inhibition efficiencies. The porosity of formed oxide film directly had impact on corrosion inhibition process as it led to localized reactions on substrate. Morphological examination of corroded substrates revealed that RSO was less prone to local corrosive attack. Inhibition efficiencies under the two electrochemical techniques employed corroborated, and corrosion inhibition occurred by retarding charge transfer reactions.