Inhibition of Al corrosion in 0.5 M HCl solution by Areca flower extract

Abstract

The corrosion inhibition property of Areca flower extract species on the Al surface in acid (0.5 M HCl) medium was tested by weight loss, Tafel plot, impedance, scanning electron microscopy and atomic force microscopy techniques. The influence of different concentrations of Areca flower extract, 0.5 M HCl solution temperature and aluminum immersion (contact) time was also evaluated. Parameters such as Ea, ΔH∗, ΔS∗, Kads and ΔG°ads were calculated by the gravimetric (weight loss) technique. Results of mass loss technique indicated that, the Areca flower extract molecules are strongly adsorbed at Al- 0.5 M HCl solution interface and follows the law of the Langmuir adsorption model. Tafel curves show that, the Areca flower extract molecules effectively adsorbed on the active Al sites by replacing the H2O molecules and strongly interact with cathodic and anodic sites impeding the dissolution reaction by mixed mode. Hence, Al metal is protected. Electrochemical impedance results indicate that, area of a semicircle (Nyquist plots) in the presence of the Areca flower extract is high compared to the bare system. The variation in the surface topography of aluminum was analyzed through scanning electron microscopy and atomic force microscopy techniques. Further, AFM results show that, surface roughness values in the protected Al system are low compared to the unprotected Al system. Keywords: Aluminum, Areca flower, Hydrochloric acid, Langmuir adsorption model, Surface morphology