Gravimetric and Electrochemical Assessments of the Corrosion Inhibition Potential of Cola nitida Seeds Extract on Mild Steel Surface in Hydrochloric Acid (HCl) Solution

Abstract

Mild steel corrosion inhibition in 1 M HCl solution by semi-pure seeds extracts of Cola nitida was investigated using gravimetric and electrochemical (potentiodynamic polarization) methods. The results obtained reveal that dichloromethane (DCM) semi-pure seeds extracts of C. nitida coded Mb4 and Mb5) inhibited mild steel corrosion in hydrochloric acid solution. The inhibition efficiency, by the gravimetric method, increased with increase in the extracts concentration but decreased with increase in temperature. The inhibition efficiency by the potentiodynamic polarization also increased with increase in extract concentration. The evaluated thermodynamic parameters revealed that the corrosion inhibition process was spontaneous and endothermic in nature. Potentiodynamic polarization measurements revealed that the extracts were mixed – type inhibitors since E_corrvalues were less than the threshold value of 85 mV. The adsorption of the extracts onto mild steel surface fitted the Temkin adsorption isotherm. Scanning electron micrographs revealed the formation of protective dense film on the steel surface in the presence of the extracts compared to the blank. Physical adsorption has been proposed for the adsorption of C. nitida seeds extracts onto mild steel surface.