Capparis aegyptia as a green inhibitor for aluminum corrosion in alkaline media

Abstract

The study of metal corrosion is of particular importance for the environment, economy and industry. Several methods have been used to control corrosion of metals. However, plant extracts are considered among the best choices as they are environmentally safe, inexpensive and renewable. In this study, the inhibition effect of Capparis Aegyptia extract on the corrosion of aluminum in 1 M sodium hydroxide (NaOH) was investigated. Both weight-loss measurements and electrochemical polarization methods were used. The results show that C. aegyptia extract is a good corrosion inhibitor. The inhibition efficiency increases with inhibitor (C. aegyptia extract) concentration and slightly increases with temperature. The inhibition efficiency reaches a maximum value of 93.8% with the highest extract concentration at 25°C. The adsorption of C. aegyptia extract on aluminum surface obeys Langmuir and Temkin adsorption isotherms. The thermodynamic adsorption free energy 0 (ΔGads) value and sign were indicative of the physisorption of C. aegyptia extract molecules on the aluminum surface. Moreover, the thermodynamic parameters (ΔH*, ΔS* and Ea) of the adsorption process were calculated and discussed. The electrochemical polarization study showed that C. aegyptia extract act as a mixed-type inhibitor cathodic and anodic. Moreover, surface morphology was analyzed by scanning electron microscopy (SEM) technique. SEM results provided confirmatory evidence of the improved surface condition, due to the adsorption, for the corrosion protection.