Adsorption and Thermodynamic Studies of Watermelon Seed Ethanol Extract on the Corrosion Inhibition of Zinc in Nitric Acid

Abstract

The corrosion inhibition potentials of ethanol extracts of watermelon seed (WSE) was investigated. The inhibition properties were investigated using weight loss measurement; Fourier transforms infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The results obtained showed that the corrosion inhibition efficiency increases with increase in the concentration of the WSE. 0.10 % v/v concentration of WSE showed a maximum corrosion inhibition efficiency of 42.4551 % at 28±1 °C. The adsorption data were modeled with Langmuir, Freundlich, Frumkin, Temkin and Flory-Huggins isotherm models with the Langmuir isotherm having the best fit (R2 0.998 – 0.999). it was more fitted to Freundlich isotherm. The adsorption process indicated feasible and spontaneous process from the large negative values of ΔGads. The values of ΔHads are all negative indicating exothermic process of adsorption. The results of FT-IR spectra showed that the inhibitor compounds were adsorbed on the zinc surface. The SEM micrographs result showed the formation of adsorbed inhibitor compounds on the zinc surface. The WSE was found to be effective and reduced the corrosion rate of zinc in nitric acid.