Anti-corrosion Process of Epiphyllum oxypetalum Extract on Aluminum Alloy in Acidic Environment

Abstract

Major problems encountered in industries, science and engineering is corrosion failure. The gravimetric, the electrochemical impedance spectroscopy (EIS) technique and Vickers hardness test were employed in investigating the anti-corrosion process of Aluminum alloy in acidic environment (0.5 M HCl solution) using Epiphyllum oxypetalum leaf extract. The leaf extraction was prepared using reflux set-up. Addition of the leaf extract in the corrosive media significantly reduced the mass loss and the corrosion (damage) rate. The inhibition efficiency increased linearly with the inhibitor concentration with a peak value of 89% for gravimetric technique and 87% for EIS technique, but slightly reduced with temperature rise. The charge-transfer resistance, Rct increased linearly with the increase in concentration of the inhibitor in the corrosive environment. The Vickers’s microindentation hardness test investigated revealed a preservation of the indentation value of the AA5052 exposed to inhibitive environment compared with those exposed to uninhibited environment. Surface screening was conducted and examined the surface morphology of the metals before, and after exposure to the various inhibitive solution. The experimental data obeyed Langmuir adsorption isotherm. Thermodynamic parameters (heat of adsorption, ∆H*, activation energy, Ea, entropy, ∆S* and Gibb’s free energy, ∆Gads) were evaluated through the Eying and Arrhenius plots. Upon the addition of the inhibitor, ∆H and Ea increased while the ∆S* decreased.