The inhibiting effect of Ailanthus altissima aqueous extract, as a corrosion inhibitor for Zn in a 0.5 M HCl solution, has been evaluated by weight loss (WL), hydrogen evolution (HE), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Obtained results showed that this extract offered good protection against Zn corrosion, and exhibited high inhibition efficiencies. The IE was found to increase with an increasing extract dose. Results revealed that this extract acted as a mixed-type inhibitor, and adsorbed onto the Zn surface following Temkin isotherm. Obtained results were justified from the study of surface morphology.Keywords: ailanthus altissima extract; HCl; Zn, corrosion inhibition, WL, HE, PP, EIS, EFM and surface morphology.
IntroductionA corrosion inhibitor is a chemical that interacts well with a metal surface, by an adsorption process, to form a thin film/layer that protects the metal surface reducing the movement/diffusion of ions to the latter, or increasing its electrical resistance [1][2]. Zn is one of the most important non-ferrous metals, which finds extensive use in metallic coating. Zn corrodes in a solution with a pH lower than 6 and higher than 12.5, but, within this range, the corrosion is very slow [3]. Under aggressive conditions, Zn metal undergoes corrosion, gaining white colored rust [4,5]. Normally, white rust is observed in galvanized materials, and its occurrence remains a serious commercial problem. In controlling or slowing down the formation of white rust, the search for new inhibitors is essential [6]. A significant method to protect the metals from corrosion is the addition of species