Spectroscopic characterization and evaluation of tender Theobroma cacao pod extract as ecofriendly inhibitor for mild steel in 1 M HCl

Theobroma cacao L. tender pod was extracted with methanol to prepare tender cacao pod extract (TCPE) using Soxhlet extraction and was characterized by Fourier transform infrared spectroscopy, and gas chromatography-mass spectroscopy. The thermal stability of TCPE was studied by thermogravimetric analysis-differential thermal analysis. The study revealed TCPE to possess heteroatoms required for the adsorption and corrosion inhibition. The TCPE was tested for its corrosion mitigating efficiency for mild steel in 1.0 M HCl by weight loss method (303-308 K), electrochemical impedance spectroscopy, and potentiodynamic polarization (303 K) methods. The inhibition efficiency of TCPE was found to increase with increase in % volume of the TCPE and decrease with increase in temperature. Impedance study showed that the values of resistance due to charge transfer (R-ct) increased with % volume of TCPE proving the corrosion inhibition on metal surface. Tafel plots showed that TCPE acts as a mixed type inhibitor. Scanning electron microscope images of the mild steel surface confirmed that TCPE acts as inhibitor by adsorption mechanism. [GRAPHICS]

Automated summary

The study characterized tender cacao pod extract (TCPE) through Fourier transform infrared spectroscopy and gas chromatography-mass spectroscopy, and investigated its thermal stability using thermogravimetric analysis-differential thermal analysis. The research revealed that TCPE has good corrosion inhibition efficiency, which increases with the percentage volume of TCPE.