Matured Theobroma Cocoa Pod Extracts as Green Inhibitor for Acid Corrosion of Aluminium

Abstract

Matured Cocoa Pod Extract (MCPE) is prepared using Soxhlet extraction and is then characterized using Fourier Transform-Infra Red Spectroscopy (FT-IR), Gas Chromatography-Mass Spectroscopy (GC-MS). The thermal decomposition characteristics are studied using Thermo Gravimetric Analysis- Differential Thermal Analysis (TGA-DTA) method. FT-IR study confirmed the presence of hetero atoms like O, N, and GC-MS showed the presence of 15 chemical constituents of which 1,2-bis (trimethylsilyl) benzene is the major constituent present. TGA-DTA studies showed the thermal decomposition of chemical constituents which was supported by GC-MS data. The inhibition efficiency of MCPE is tested in 0.5M HCl medium taking aluminum as the target metal by Weight loss method (303K-308K). The anticorrosive property of MCPE was also tested using Electrochemical Impedance Spectroscopy and Potentiodynamic Polarization methods (303K). In all the methods, the inhibition efficiency of MCPE was found to increase with an increase in % volume of the MCPE exhibiting good agreement with each other. Also, inhibition efficiency decreased with an increase in temperature, showing adsorption of inhibitor is by physisorption and thermodynamic parameters are measured. Tafel plots showed MCPE could retard both anodic and cathodic reactions, predominantly acting as an anodic type of inhibitor. Surface morphological changes of the metal were studied using Scanning Electron Microscopy which confirmed that MCPE acted as an inhibitor by adsorption mechanism.