Inhibition Efficiency of Eco-friendly Green Inhibitors (Ocimum tenuiflorum Phytocompounds) on Corrosion of High Carbon Steel in HCl Environment using Thermometric and Electrochemical Methods

Abstract

Corrosion inhibition behavior of crude alkaloids and flavonoids extracts of Ocimum tenuiflorum roots on the corrosion of high carbon steel in hydrogen chloride acid environment was studied using thermometric, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The phytocompounds showed excellent corrosion retardation ability on the high carbon steel metal in HCl acid environment. The alkaloids demonstrated a more reliable inhibition efficacy compared to flavonoids extracts with maximum inhibition efficiency of 98.1% and 93.6% respectively at a maximum concentration of 2.0 g/L. There was a noticeable increase in inhibition mitigation potential of the inhibitors with increasing concentration of extracts. A physical adsorption mechanism was recorded by the inhibitor and the Langmuir adsorption isotherm was well obeyed with correlation coefficient (R2) at approximately 0.999. Results of electrochemical impedance spectroscopy and potentiodynamic polarization confirmed the strong adsorption of the inhibitors on the steel surface through the values of charge transfer resistance and corrosion current densities. The inhibitors proved to be stable ones on the metal and a spontaneous reaction process was recorded from the data derived from the Gibbs free energy of adsorption.