J. Indian Chern. Soc., Vol. 90, July 2013, pp. 1009-1014 Inhibition effect of glycine towards the corrosion of mild steel Y. Brightson Arul Jacob 0 , J. Jeyasundari 0 *, R. Sayee Kannanb and A. Jawahar 0 0 Department of Chemistry, NMSSVN College, Madurai-625 019, Tamilnadu, India E-mail : jjsundari16@yahoo.com boepartment of Chemistry, Thiagarajar College, Madurai-625 009, Tamilnadu, India Manuscript received online 13 July 2011, revised 17 August 2012, accepted 20 August 2012 Abstract : Inhibition effect of glycine towards the corrosion of mild steel was investigated using potentiodynamic polari- zation and electrochemical impedance spectroscopy (EIS) techniques. It was found that these investigated compounds act as good inhibitors for the corrosion of mild steel in 250 ppm of glycine and 50 ppm of zn2+. EIS was used to investigate the mechanism of corrosion inhibition. The addition of zn2+ was found to have a synergistic effect which enhanced the inhibition efficiency. Keywords : Corrosion, mild steel, glycine, zn2+. Introduction Amino acids form a class of non toxic organic com- pounds. These properties would justify their use as cor- rosion inhibitors. The inhibitors are used in protection against the corrosion of certain metals such as nickel, cobalt, copper, iron and steel. All amino acids have a central or alpha carbon, to which are bonded four groups; hydrogen, an amino, a carboxyl group, and a unique side chain, also known as R-group 1 • 2 . The adsorption of amino acid on carbon steel in acidic environment has been in- vestigated by Akiyama and Nobe3. Additional amino group or groups which increased electron density on the alpha amino group also increased the inhibition efficiency 4 . These molecules differ in their unique side chain, which can be used to classify the molecules into functional types. Cystein, alanine and phenylalanine have been used to in- hibit the corrosion of bronze in an aqueous solution con- taining sodium sulphate and sodium bicarbonate5-8. Cystein, glycine, glutamic acid and glutathione have been used as corrosion inhibitor to prevent the corrosion of copper in HC1 9 . The corrosion of brass in 0 2 -free NaOH has been prevented by methionine 10 . Amino acids have been used to prevent chloride-induced corrosion in rein- forced concrete structure 11 • 12 . Amino acids such as phe- nylalanine have been used to prevent corrosion of Mg- Al-Zn alloy in chloride-free neutral solution 13 . The electro- chemical behaviour of cysteine has been studied by cyclic voltammetry 14 • 15 . Glycine dimethyl phosphonic acid is mainly used as corrosion inhibitor for industrial circulat- ing cool water system. It is a new kind of organophosphine corrosion inhibitor. It shows certain antiscale ability and better corrosion inhibition as there are both carboxyl group and nitrogen phosphorus atoms in it. The aim of this research is to investigate the inhibitive effect of amino acid such as glycine. For this purpose potentiodynamic polarization and impedance spectroscopy have been used in the present study. The present work is undertaken : (i) To evaluate the inhibition efficiency of glycine in controlling corrosion of mild steel in an aqueous solution by weight loss methods. (ii) To correlate the ligand-transporting efficiency of Zn 2 + and the corrosion inhibition efficiency of glycine. (iii) To study the mechanistic aspect of corrosion inhi- bition by electrochemical studies such as polarization study, AC impedance spectra. (iv) To propose suitable mechanism of corrosion inhi- bition based on the above results. Experimental Preparation of specimens : Preparations of the mild steel specimens were chosen 1009