CORROSION INHIBITION POTENTIAL OF HEXANE, ACETONE AND ETHANOLIC EXTRACTS OF SWEET PRAYER PLANT (Thaumatococcus daniellii BENN) ON MILD STEEL IN 1 M HCl

Abstract

Corrosion is defined as a process that leads to the deterioration of metallic materials as a result of interaction with corrosive environments. Corrosion inhibitors are added to several systems as a form of protection against corrosion in a corrosive environment. The corrosion inhibitive effect of hexane, acetone and ethanolic extracts of Thaumatococcus daniellii (Benn) leaves on mild steel in hydrochloric acid solutions was investigated using electrochemical and gravimetric methods in conjunction with surface analysis by scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy. The experiments were conducted at varying concentrations (0−10 x 103 ppm) of extracts, temperature (298−323 K) and immersion times (24−96 h). The adsorption isotherm studies were conducted using the Langmuir, Freundlich, Temkin and El-Awady models. Results obtained included Electrochemical Impedance Spectroscopy, Potentiodynamic Polarisation, kinetic, thermodynamic, and adsorption parameters. The results revealed that the ethanolic extract of T. danielli leaves had the highest corrosion inhibitory potential as it contained more corrosion inhibitory organic compounds. The kinetic data of the corrosion process followed first order kinetic model. It was confirmed by potentiodynamic polarisation measurements that the three extracts (hexane, acetone and ethanolic) were mixed-type inhibitor by action. The corrosion process was endothermic and spontaneous with a level of disorderliness. The SEM micrographs displayed the roughness of the metal surface in the absence of the three extracts and the smoothness in the presence of the extracts. Important functional group bands of the phytochemicals were revealed in the FTIR spectra