Inhibition of Corrosion of Aluminium in Potassium Hydroxide Solution by Pyridine Derivatives

The influence of 3-methylpyridine and 3-nitropyridine on the corrosion rate of aluminium in 1？mol？L？1 potassium hydroxide solution was investigated using weight loss method. It was observed that both investigated derivatives behave as inhibitors. It was found that the inhibition efficiency increases with increasing inhibitor concentration. The inhibition mechanism is discussed on the basis of adsorption of inhibitor molecules on the metal surface. The inhibitors were adsorbed on the surface according to the Frumkin adsorption isotherm. The effect of temperature on the corrosion inhibition of Al was studied and thermodynamic functions for the dissolution and adsorption processes in the absence and in the presence of the inhibitors were computed and discussed. 1. Introduction Aluminium is widely used in industry because of its low density, pleasing appearance, and corrosion resistance nature. During industrial process it often comes in contact with corroding solutions. Therefore, corrosion creates serious troubles in the industry [1]. For these reasons, various workers have explained the corrosion inhibition of aluminium in different solutions [2–10]. A useful method to protect metals deployed in service in corrosive environment is the adsorption of species on the surface of metal in order to inhibit the corrosion reaction and reduce the corrosion rate. The extent of adsorption depends on the nature of the metal, the condition of the metal surface, the mode of adsorption, the chemical structure of the inhibitor, and the type of corrosive media [11]. Among the various methods used in treating corrosion problems, the use of chemical inhibitors is the most cost effective and practical method. The use of corrosion inhibitors based on organic compounds containing nitrogen, sulfur, and oxygen atoms is of growing interest in the field of corrosion and industries, as corrosion causes serious problems to the service lifetime of alloys used in industry [12]. The stability of the adsorbed inhibitor films formed on the metal surface to protect the metal from corrosion depends on physicochemical properties of the molecule, such as aromaticity, steric effects, electron density of donor atoms, as well as the type of corrosive medium, and the nature of the interaction between the inhibitor and the metal surface [13–15]. A number of organic compounds are known to be applicable as corrosion inhibitors in alkaline environment. However there is no report on influence of pyridine derivatives as corrosion inhibitors. As a part of our contribution to the growing interest of