%0 Journal Article
%T Study of Synergistic Effect of Iodide on the Corrosion Antagonistic Behaviour of a Heterocyclic Phenylhydrazone in Sulphuric Acid Medium on Carbon Steel
%A Vinod P. Raphael
%A Joby Thomas Kakkassery
%A Shaju K. Shanmughan
%A Aby Paul
%J ISRN Corrosion
%D 2013
%R 10.1155/2013/390823
%X Synergistic effect of KI on the corrosion inhibition efficiency of 3-acetylpyridine phenylhydrazone (3APPH) on carbon steel (CS) in 0.5£¿M sulphuric acid solution has been investigated using gravimetric studies, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies. Gravimetric corrosion studies revealed that 3APPH showed moderate corrosion inhibition efficiency up to 8£¿h and beyond this period it showed corrosion accelerating behavior. This antagonistic effect of 3APPH is due to the hydrolysis of the molecule in acidic medium. A very high percentage of inhibition efficiency at 24£¿h was obtained on the addition of KI due to the synergistic effect of iodide ions. The adsorption of 3APPH and 3APPH£¿+£¿KI on the surfaces of the corroding metal obey Langmuir isotherm as obtained by impedance measurements. Polarization studies revealed that 3APPH act as a mixed type inhibitor. Thermodynamic parameters ( ) were derived from the adsorption isotherms. Surface morphology of the corroding metal was investigated by SEM analysis. 1. Introduction Industrial processes such as pickling and descaling will escalate the corrosion rate of metals enormously and the addition of certain organic compounds which contain -bonds and heteroatoms like N, O, and S is considered as the most useful method for reducing the corrosion of carbon steel in acidic media [1¨C3]. Molecules equipped with the above mentioned active probes may not act as a good inhibitors against corrosion in severe aggressive solutions such as sulphuric acid. It has been found that the addition of halide ions to the sulphuric acid enhance the corrosion inhibition capacity of the organic molecules on carbon steel synergistically. The synergistic effect of the halides has increased [4, 5] in the order Cl£¿ < Br£¿ < I£¿. Due to large size and ease of polarizability, iodide (I£¿) shows the highest synergistic effect [6¨C10]. The present study was conducted to examine the corrosion response of carbon steel in sulphuric acid containing the phenylhydrazone 3APPH and the synergistic behavior of 3APPH with I£¿ on the corrosion of carbon steel [11¨C13]. 2. Experimental 2.1. Synthesis The heterocyclic phenylhydrazone (3APPH) was obtained by the condensation of equimolar mixture of 3-acetylpyridine and phenylhydrazine hydrochloride in ethanol. The reaction mixture was refluxed for 2 hours, cooled to obtain yellow precipitate, filtered, washed with water, and dried. Figure 1 shows the molecular structure of phenylhydrazone 3APPH. Anal. calcd for C13H13N3: C, 73.93; H, 6.16; N, 19.9%. Found C, 73.47; H,
%U http://www.hindawi.com/journals/isrn.corrosion/2013/390823/