Corrosion Behavior of Environmental Friendly Inhibitor of Theobroma cacao Peels Extract for Mild Steel in NaCl 1.5 M

Abstract

In this investigation, the inhibition effect of TCPE (Theobroma cacao peels extract) on mild steel in NaCl 1.5 M solution has been studied by using weight loss, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) methods. Infrared spectra and GC-MS performed to determine the extract compounds that played a role in the inhibition process. Sample surface morphology was observed by using a scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The obtained changes in polarization and impedance parameters values (Icorr, Rct and Cdl) that has been obtained indicate that the adsorbed protective film grew with the sign of increasing concentration of inhibitor. The adsorption of used compound on mild steel found to obey Langmuir isotherm. Some thermodynamic parameters such as Gibs energy (ΔG), enthalpy (ΔH), entropy (ΔS) and activation energy (Ea) were calculated to elaborate the mechanism of corrosion inhibition. Based on the results of surveying activity, it revealed that the corrosion rate decreased with the increase of the extract concentration and increased with increasing temperature. Corrosion inhibition efficiency of 91.93 (weight loss) and 85.90% (Tafel), 90.19% (Rp) and 75.23% (EIS) were at a concentration of 2.5% extract. The Schiff base used for investigation was considered an effective inhibitor in reducing the attack surface corrosion on mild steel. in NaCl 1.5 M solution. The obtained results from various techniques were in good agreement.

Keywords

• Theobroma cacao peels extract
• corrosion inhibitor
• Tafel
• adsorption
• GC-MS