Capparis decidua : A Green Inhibitor for Pure Aluminum Corrosion in Basic Media

Aluminum corrosion inhibition using Capparis decidua extract has been studied. The study was performed in a 1.0 M solution of sodium hydroxide and was monitored both by measuring mass-loss and by using electro-chemical and polarization methods. In addition, surface morphology analysis was performed by applying the technique of Scanning Electron Microscopy (SEM). Results demonstrate effectiveness of Capparis decidua extract as an inhibitor and the efficiency is both concentration and temperature dependent. Optimum (95.2%) inhibitor efficiency was found with maximum extract concentration at 45˚C. Results also show a slight decrease of aluminum dissolution upon increasing temperature using Capparis decidua extract. Based on Langmuir adsorption model, Capparis decidua adsorption on aluminum surface shows a high regression coefficient value. Based on the observed results, the activation enthalpy (ΔH#) and activation entropy (ΔS#) have been estimated and discussed. The value, and sign, of the thermodynamic adsorption free energy (ΔGoads) indicate that Capparis decidua extract undergoes physisorption on aluminum surface. A mixed-type inhibition of Capparis decidua extract has been concluded from electrochemical polarization studies. The study clearly shows that Capparis decidua extract acted against aluminum corrosion in alkaline media by forming a protective film on the top of aluminum surface which was determined by SEM results.