Adsorption Properties and Electrochemical Behavior of Thymus Willdenowii Boiss and Reut Essential Oil as a Green Inhibitor for Mild Steel Corrosion in 1 M HCl

Abstract

The inhibition effect of Thymus willdenowii Boiss & Reut essential oil (TW) on the mild steel corrosion in 1 M HCl has been investigated using weight loss measurements, surface analysis (SEM-EDX, three-dimensional profilometry and FT-IR), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The TW oil anticorrosion effect was evaluated using polarization potentiodynamic curves obtained after 30, 60 and 90 min of immersion in a 1 M HCl medium. Gravimetric results have shown that TW oil has a significant inhibition efficiency value of 81.42%, which was attained at 3 g/L. The polarization measurements have shown that TW is a mixed type inhibitor, with a significant reduction in cathodic and anodic current densities. Measurements by electrochemical impedance spectroscopy revealed that resistance to the charge transfer has increased with higher TW oil concentrations. From the use of SEM-EDX and three-dimensional profilometry, it is clear that the metal surface has remarkably improved in the TW oil presence, compared to the one exposed to the acid medium without essential oil. From the TW proprieties and the obtained results, it can be concluded that this oil is a new natural substance that can be used against material corrosion in aggressive solutions.