Electrochemical and computational study of gum exudates from Canarium schweinfurthii as green corrosion inhibitor for mild steel in HCl solution

摘要

The inhibition efficiency of the corrosion on mild steel in acid by Canarium schweinfurthii (CS)gum as inhibitor has been studied using chemical techniques (thermometric, gasometric, spectrophotometricand weight loss) and electrochemical techniques (electrochemical impedancespectroscopy (EIS) and potentiodynamic polarization (PDP)). Scanning Electron Spectroscopy(SEM) was used to examine the surface morphology of mild steel samples both in the presenceand absence of inhibitors at optimum conditions. Results obtained indicated that CSinhibited the corrosion of mild steel in HCl. The inhibition efficiency increases with increasingthe inhibitor concentration but decreases with increasing the temperature. CS behavedas mixed type inhibitor retarding both cathodic and anodic reaction with high inhibition efficiency.Gas chromatography mass spectrometer (GCMS) spectrum of CS gum showed thepresence of Nonacosane; 1-piperoylp; Stearic acid, 2-(hydroxymethyl)-2-nitropropane-1,3-diol,Stigmasta-5,22-dien-3-ol, dihex-5-en-2-yl phthalate, 9-octadecenoic acid, methyl ester,, 1-pentadecarecarboxylicand Oleic acid. Inhibition action of the gum gave a strong correlation with thesephytochemicals in the gum. Phenomenon of physical adsorption was proposed for the inhibitionand the process followed the Langmuir adsorption isotherm with very high negative valuesof the free energy of adsorption (Gads). Both the chemical and electrochemical results are ingood agreement with each other while the surface studies reveal the formation of a smooth,dense protective layer in the presence of inhibitor. Quantum chemical computations of parametersassociated with the electronic structures of specific components of the gum supported theirinhibiting potentials.