Garcinia indica as an Environmentally Safe Corrosion Inhibitor for Aluminium in 0.5？M Phosphoric Acid

The Inhibitive and adsorption properties of aqueous extract of seeds of Garcinia indica extract (GIE) have been studied for corrosion control of aluminium in 0.5？M phosphoric acid solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques at to . The effects of inhibitor concentration on the inhibition action were investigated. Polarization measurements showed that the GIE acted as mixed inhibitor and the inhibitor molecules followed chemical adsorption on the surface of aluminium. The adsorption of GIE on metal surface obeyed Langmuir adsorption isotherm. The surface morphology of aluminium, in the absence and in the presence of GIE in 0.5？M phosphoric acid solution, was studied using scanning electron microscopy (SEM). Results obtained from both of the electrochemical techniques were in good agreement with each other. 1. Introduction Aluminium is the most commonly used metal in power transmission and the metallurgy of nonferrous metals due to its high-electrical conductivity, good working and forming properties, lightness, ease of recycling, low density, ductility, and high-mechanical strength [1, 2]. Aluminium and most of the aluminium alloys have good corrosion resistance towards natural atmosphere and other environments, because aluminium surfaces are covered with a natural oxide film. In the presence of aggressive environment the protective layer can be locally destroyed and corrosive attack takes place. Solutions of phosphoric acid are frequently employed for cleaning of aluminium [3] and in commercial preplating anodic oxidation and electropolishing of aluminium [4]. Phosphoric acid is most preferred for metal cleaning than hydrochloric [5] or sulphuric acid because of lower dissolution of metal in phosphoric acid medium. Even though dissolution rate of aluminium in phosphoric acid is lower, it is not at all negligible [6]. Therefore, it is necessary to use inhibitors for the corrosion of aluminium in phosphoric acid solution [7–10]. Among the numerous organic compounds that have been tested and are applied industrially as corrosion inhibitors, those that are nontoxic are now far more strategic than in the recent past [7–11]. In the past two decades the research in the field of green inhibitors has been addressed toward the goal of using cheap, effective molecules at low or zero environmental impact [12–18]. In an attempt to find corrosion inhibitors that are environmentally safe and readily available, there has been a growing trend in the use of natural products such as plants extracts as corrosion