ABSTRACT Studies on surface analysis of carbon steel protected from corrosion in low chloride and nearly neutral aqueous environment by a synergistic mixture containing N,N-bis(phosphonomethyl) glycine (BPMG), zinc ions and citrate ions are presented. The effect of addition of citrate to the binary system, BPMG-Zn2+, is quite significant and is well explored through various studies. The surface protective nature is maintained in the pH range 5-9. Potentiodynamic polarization studies inferred that the ternary inhibitor is a mixed inhibitor. Impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the chosen environment. X-ray photoelectron spectroscopic (XPS) analysis of the surface film showed the presence of the elements namely iron, phosphorus, nitrogen, carbon, oxygen and zinc. Deconvolution spectra of these elements in the surface film inferred the presence of oxides/hydroxides of iron(III), Zn(OH)2 and [Fe(III), Zn(II)-BPMG-citrate] heteropolynuclear multiligand complex. This inference is further supported by the reflection absorption Fourier transform infrared spectrum of the surface film. Analysis by scanning electron microscopy (SEM) is presented for both the corroded and protected metal surfaces. Based on all these results, a plausible mechanism of corrosion inhibition is proposed.
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B. Rao, M. Rao, S. Rao and B. Sreedhar, "Surface Analysis of Carbon Steel Protected from Corrosion by a New Ternary Inhibitor Formulation Containing Phosphonated Glycine, Zn2+ and Citrate," Journal of Surface Engineered Materials and Advanced Technology, Vol. 3 No. 1, 2013, pp. 28-42. doi: 10.4236/jsemat.2013.31005.
 D.-J. Choi, S.-J. You and J.-G. Kim, “Development of an Environmentally Safe Corrosion, Scale, and Microorganism Inhibitor for Open Recirculating Cooling Systems,” Materials Science and Engineering: A, Vol. 335, No.1-2, 2002, pp. 228-235.
 H. Amar, J. Benzakour, A. Derja, D. Villemin and B. Moreau, “A Corrosion Inhibition Study of Iron by Phosphonic Acids in Sodium Chloride Solution,” Journal of Electroanalytical Chemistry, Vol. 558, 2003, pp. 131-139. doi.org/10.1016/S0022-0728(03)00388-7
 H. S. Awad and S. Turgoose, “Influence of Hardness Salts on Effectiveness of Zinc-1-Hydroxyethylidene-1,1-Diphosphonic Acid (HEDP) Mixtures in Inhibiting the Corrosion of Mild Steel in Neutral Oxygen-Containing Solutions,” Corrosion, Vol. 60, No. 12, 2004, pp. 1168-1179. doi.org/10.5006/1.3299230
 K. D. Demadis, S. D. Katarachia and M. Koutmos, “Crystal Growth and Characterization of Zinc-(Amino-Tris-(Methylenephosphonate)) Organic-Inorganic Hybrid Networks and Their Inhibiting Effect on Metallic Corrosion,” Inorganic Chemistry Communications, Vol. 8 No. 3, 2005, pp. 254-258.
 I. Felhosi, Zs. Ke-resztes, F. H. Karman, M. Mohai, I. Bertoti and E. Kalman, “Effects of Bivalent Cations on Corrosion Inhibition of Steel by 1-Hydroxyethane-1,1-Diphosphonic Acid,” Journal of The Electrochemical Society, Vol. 146, No. 3, 1999, pp. 961-969.
 Y. Gonzalez, M. C. Lafont, N. Pebere and F. Moran, “A Synergistic Effect between Zinc Salt and Phosphonic Acid for Corrosion Inhibition of a Carbon Steel,” Journal of Applied Electrochemistry, Vol. 26, No. 12, 1996, pp. 1259-1265. doi.org/10.1007/BF00249928
 M. A. Pech-Canul and L. P. Chi-Canul, “Investigation of the Inhibitive Effect of N-Phosphono-Methyl-Glycine on the Corrosion of Carbon Steel in Neutral Solutions by Electrochemical Techniques,” Corrosion, Vol. 55, No. 10, 1999, pp. 948-956. doi.org/10.5006/1.3283931
 M. A. Pech-Canul and P. Bartolo-Perez, “Inhibition Effects of N-Phosphono-Methyl-Glycine/Zn2+ Mixtures on Corrosion of Steel in Neutral Chloride Solutions,” Surface and Coatings Technology, Vol. 184, No. 2-3, 2004, pp. 133-140. doi.org/10.1016/j.surfcoat.2003.11.018
 S. Rajendran, B. V. Appa Rao and N. Palaniswamy, “Synergistic Effect of 1-Hydroxyethane-1,1-Diphosphonic Acid and Zn2+ on the Inhi-bition of Corrosion of Mild Steel in Neutral Aqueous Environ-ment,” Anti-Corrosion Methods and Materials, Vol. 46, No. 1, 1999, pp. 23-28.
 L. Y. Reznik, L. Sathler, M. J. B. Car-doso and M. G. Albuquerque, “Experimental and Theoretical Structural Analysis of Zn(II)-1-Hydroxyethane-1,1-Diphosphonic Acid Corrosion Inhibitor Films in Chloride Ions Solution,” Materials and Corrosion, Vol. 59, No. 8, 2008, pp. 685-690. doi.org/10.1002/maco.200804108
 A. Shaban, E. Kalman and I. Biczo, “Inhibition Mechanism of Carbon Steel in Neutral Solution by N-Phosphono-Methyl-Glycine,” Corrosion Science, Vol. 35, No. 5-8, 1993, pp. 1463-1470.
 J. Telegdi, M. M. Shaglouf, A. Shaban, F. H. Karman, I. Betroti, M. Mohai and E. Kalman, “Influence of Cations on the Corrosion Inhibition Efficiency of Aminophosphonic Acid,” Electrochimica Acta, Vol. 46, No. 24-25, 2001, pp. 3791-3799.
 H. S. Awad, “The Effect of Zinc-to-HEDP Molar Ratio on the Effectiveness of Zinc-1-Hydroxyethylidene-1,1-Diphosphonic Acid in Inhibiting Corrosion of Carbon Steel in Neutral Solutions,” Anti-Corrosion Methods and Materials, Vol. 52, No. 1, 2005, pp. 22-28.
 J. Jaworska, H. V. Genderen-Takken, A. Hanstveit, E. Plassche and T. Feijtel, “Environmental Risk Assessment of Phosphonates, Used in Domestic Laundry and Cleaning Agents in the Netherlands,” Chemosphere, Vol. 47, No. 6, 2002, pp. 655-665.
 B. V. Appa Rao, M. Venkateswara Rao, S. Srinivasa Rao and B. Sreedhar, “Synergistic Effect of N,N-Bis(Phosphonomethyl) Glycine and Zinc Ions in Corrosion Control of Carbon Steel in Cooling Water Systems,” Chemical Engineering Communications, Vol. 198, 2011, pp. 1505-1529. doi.org/10.1080/00986445.2010.525200
 S. Westerback, K. S. Rajan and A. E. Martell, “New Multidentate Ligands. III. Amino Acids Containing Methylenephosphonate Groups,” Journal of American Chemical Society, Vol. 87, No. 12, 1965, pp. 2567-2572.
 P. Amico, P. G. Daniele, V. Cucinotta, E. Rizzarelli and S. Sammartano, “Equilibrium Study Of Iron(II) and Manganese(II) Complexes with Citrate Ion in Aqueous Solution: Relevance to Coordination of Citrate to the Active site of Aconitase and to Gastrointestinal Absorption of Some Essential Metal Ions,” Inorganica Chimica Acta, Vol. 36, 1979, pp. 1-7.
 S. R. Hurford, C. R. Morris, J. A. Vesey, D. R. Williams, D. Cummins, P. I. Riley, G. L. Christie and J. R. Duffield, “Thermodynamic Formation Constants and Solid State Properties for the Interaction of Zn(II) Ions with Citrate, Phenolsulphonate, Monofluorophosphate, and Saccharinate,” Journal of Inorganic Biochemistry, Vol. 42, No. 4, 1991, pp. 273-287.
 L-C Konigsberger, E. Konigsberger, P. M. May and G. T. Hefter, “Complexation of Iron(III) and Iron(II) by Citrate. Implications for Iron Speciation in Blood Plasma,” Journal of Inorganic Biochemistry, Vol. 78, No. 3, 2000, pp. 175-184. doi.org/10.1016/S0162-0134(99)00222-6
 ASTM Standard G31-72(1999), “Standard Practice for Laboratory Immersion Corrosion Testing of Metals,” ASTM International, West Conshohocken, 2004.
 R. A. Freeman and D. C. Silverman, “Error Propagation in Coupon Immersion Tests,” Corrosion, Vol. 48, No. 6, 1992, pp. 463-466. doi.org/10.5006/1.3315961
 M. Elachouri, M. S. Hajji, M. Salem, S. Kertit, J. Aride, R. Coudert and E. Essassi, “Some Nonionic Surfactants as Inhibitors of the Corrosion of Iron in Acid Chloride Solutions,” Corrosion, Vol. 52, No. 2, 1996, pp. 103-108.
 S. Rajendran, S. M. Reenkala, N. Anthony and R. Ramaraj, “Synergistic Corrosion Inhibition by the Sodium Dodecylsulphate-Zn2+ System,” Corrosion Science, Vol. 44, No. 10, 2002, pp. 2243-2252.
 B. V. Appa Rao, S. Srinivasa Rao and M. Venkateswara Rao, “Environmentally Friendly Ternary Inhibitor Formulation Based on N,N-Bis(Phosphonomethyl) Glycine,” Corrosion Engineering Science and Technology, Vol. 43, No. 1, 2008, pp. 46-53.
 S. L. Li, H. Y. Ma, S. B. Lei, R. Yu, S. H. Chen and D. X. Liu, “Inhibition of Copper Corrosion with Schiff Base Derived from 3-Methoxysalicylaldehyde and O-Phenyldiamine in Chloride Media,” Corrosion, Vol. 54, No. 12, 1998, pp. 947-954. doi.org/10.5006/1.3284816
 K. Juttner, “Electrochemical Impedance Spectroscopy (EIS) of Corrosion Processes on Inhomogeneous Surfaces,” Electrochimica Acta, Vol. 35, No. 10, 1990, pp. 1501-1508. doi.org/10.1016/0013-4686(90)80004-8
 A. A. El Hosary, R. M. Saleh and A. M. Shams E. Din, “Corrosion Inhibition by Naturally Occurring Substances-I. The Effect of Hibiscus Subdariffa (Karkade) Extract on the Dissolution of Al and Zn,” Corrosion Science, Vol. 12, No. 12, 1972, pp. 897-904.
 F. Mansfeld, M. W. Kendig and W. J. Lorenz, “Corrosion Inhibition in Neutral, Aerated Media,” Journal of the Electrochemical Society, Vol. 132, No. 2, 1985, pp. 290-296. doi.org/10.1149/1.2113820
 X. Wu, H. Ma, S. Chen, Z. Xu and A. Sui, “General Equivalent Circuits for Faradaic Electrode Processes Under Electrochemical Reaction Control,” Journal of The Electrochemical Society, Vol. 146, No. 5, 1999, pp. 1847-1853. doi.org/10.1149/1.1391854
 M. S. Morad, “An Electrochemical Study on the Inhibiting Action of Some Organic Phosphonium Compounds on the Corrosion of Mild Steel in Aerated Acid Solutions,” Corrosion Science, Vol. 42, No. 8, 2000, pp. 1307-1326.
 G. Gunasekaran and L. R. Chauhan, “Eco Friendly Inhibitor for Corrosion Inhibition of Mild Steel in Phosphoric Acid Medium,” Elec-trochimica Acta, Vol. 49, No. 25, 2004, pp. 4387-4395.
 W. Scheider, “Theory of the Frequency Dispersion of Electrode Polarization. Topology of Networks with Fractional Power Frequency De-pendence,” The Journal of Physical Chemistry, Vol. 79, No. 2, 1975, pp. 127-136.
 H. Ma, S. Chen, X. Chen, G. Li and X. Yang, “Analysis of Impedance Data with Dispersing Effect by Using the Linear Least Squares Regression Method,” Journal of Serbian Chemical Society, Vol. 62, No. 12, 1997, pp. 1201-1212. .
 D. D. Mac Donald and M. C. H. Mckubre, “Modern Aspects of Electrochemistry,” Plenum Press, New York, 1982.
 M. Touzet, M. Cid, M. Puiggali and M. C. Petit, “An EIS Study and Auger Analysis on 304L Stainless Steel in Hot Chloride Media before and after a Sample Straining,” Corrosion Science, Vol. 34, No. 7, 1993, pp. 1187-1196.
 O. Oli-vares-Xometl, N. V. Likhanova, R. Martinez-Palou and M. A. Dominguez-Aguilar, “Electrochemistry and XPS Study of an Imidazoline as Corrosion Inhibitor of Mild Steel in an Acidic Environment,” Materials and Corrosion, Vol. 60, No. 1, 2009, pp. 14-21.
 A. Alagta, I. Felhosi, J. Telegdi, I. Bertoti and E. Kalman, “Effect of Metal Ions on Corrosion Inhibition of Pimeloyl-1,5-Dihydroxamic Acid for Steel in Neutral Solution,” Corrosion Science, Vol. 49, No. 6, 2007, pp. 2754-2766. doi.org/10.1016/j.corsci.2006.11.008
 K. F. Khaled, “The Inhibition of Benzimidazole Derivatives on Corrosion of Iron in 1M HCl Solutions,” Electrochimica Acta, Vol. 48, No. 17, 2003, pp. 2493-2503. doi.org/10.1016/S0013-4686(03)00291-3
 K. Babic-Samardzija, C. Lupu, N. Hackerman, A. R. Barron and A. Luttge, “Inhibitive Properties and Surface morphology of a Group of Heterocyclic Diazoles as Inhibitors for Acidic Iron Corrosion,” Langmuir, Vol. 21, No. 26, 2005, pp. 12187-12196.
 E. Machnikova, K. H. Whitmire and N. Hackerman, “Corrosion Inhibition of Carbon Steel in Hydrochloric Acid by Furan Derivatives,” Electrochimica Acta, Vol. 53, No. 20, 2008, pp. 6024-6032.
 C. T. Wang, S. H. Chen, H. Y. Ma and N. X. Wang, “Study of the Stability of Self-Assembled N-Vinylcarbazole Monolayers to Protect Copper against Corrosion,” Journal of Serbian Chemical Society, Vol. 67, No. 10, 2002, pp. 685-696.
 J. F. Moulder, W. F. Stickle, P. E. Sobol and K. D. Bamben, “Handbook of X-Ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data,” Physical Electronics Division, Eden Prairie, 1995.
 E. Kalman, F. H. Karman, I. Cserny, L. Kover, J. Telegdi and D. Varga, “The Effect of Calcium Ions on the Adsorption of Phosphonic Acid: A Comparative Investigation with Emphasis on Surface Analytical Methods,” Electrochimica Acta, Vol. 39, No. 8-9, 1994, pp. 1179-1182. doi.org/10.1016/0013-4686(94)E0034-W
 N. S. McIntyre and D. G. Zetaruk, “X-Ray Photoelectron Spectroscopic Studies of Iron Oxides,” Analytical Chemistry, Vol. 49, No. 11, 1977, pp. 1521-1529.
 S. Maroie, M. Savy and J. J. Verbist, “ESCA and EPR Studies of Monomer, Dimer, and Polymer Iron Phthalocyanines: Involvements for the Electrocatalysis of Molecular Oxygen Reduction,” Inorganic Chemistry, Vol. 18, No. 9, 1979, pp. 2560-2567.
 K. Asami, K. Hashimoto and S. Shimodaira, “X-Ray Photoelectron Spectrum of Fe2+ State in Iron Oxides,” Corrosion Science, Vol. 16, No. 1, 1976, pp. 35-45.
 M. Koudelka, J. Sanchez and J. Augustynski, “On the Nature of Surface Films Formed on Iron in Aggressive and Inhibiting Polyphosphate Solutions,” Journal of The Electrochemical Society, Vol. 129, No. 6, 1982, pp. 1186-1191. doi.org/10.1149/1.2124084
 N. Nakayama, “Inhibitory Effects of Nitrilotris-(Methylenephosphonic Acid) on Cathodic Reactions of Steels in Saturated Ca(OH)2 Solutions,” Corrosion Science, Vol. 42, No. 11, 2000, pp. 1897-1920.
 N. Ochoa, G. Baril, F. Moran and N. Pebere, “Study of the Properties of a Multi-Component Inhibitor Used for Water Treatment in Cooling Circuits,” Journal of Applied Electrochemistry, Vol. 32, No. 5, 2002, pp. 497-504.
 M. El Azhar, M. Traisnel, B. Mernari, L. Gengembre, F. Bentiss and M. Lagrenee, “Electrochemical and XPS Studies of 2,5-Bis(N-Pyridyl)1,3,4-Thiadiazoles Adsorption on Mild Steel in Perchloric Acid Solution,” Applied Surface Science, Vol. 185, No. 3-4, 2002, pp. 197-205.
 A. Meneguzzi, C. A. Ferreira, M. C. Pham, M. Delamar and P. C. Lacaze, “Electrochemical Synthesis and Characterization of Poly(5-Amino-1-Naphthol) on Mild Steel Electrodes for Corrosion Protection,” Electrochimica Acta, Vol. 44, No. 12, 1999, pp. 2149-2156.
 G. P. Cicileo, B. M. Rosales, F.e. Varela and J. R. Vilche, “Comparative Study of Organic Inhibitors of Copper Corrosion,” Corrosion Science, Vol. 41, No. 7, 1999, pp. 1359-1375. doi.org/10.1016/S0010-938X(98)00190-5
 K. Aramaki and T. Shimura, “Prevention of Passive Film Breakdown on Iron in a Borate Buffer Solution Containning Chloride Ion by Coverage with a Self-Assembled Monolayer of Hexadecanoate Ion,” Corrosion Science, Vol. 45, No. 11, 2003, pp. 2639-2655.
 F. H. Karman, I. Felhosi, E. Kalman, I. Cserny and L. Kover, “The Role of Oxide Layer Formation during Corrosion Inhibition of Mild Steel in Neutral Aqueous Media,” Electrochimica Acta, Vol. 43, No.1-2, 1998, pp. 69-75. doi.org/10.1016/S0013-4686(97)00236-3
 J. L. Fang, Y. Li, X. R. Ye, Z. W. Wang and Q. Liu, “Passive Films and Corrosion Protection due to Phosphonic Acid Inhibitors,” Corrosion, Vol. 49, No. 4, 1993, pp. 266-271. doi.org/10.5006/1.3316048
 K. Aramaki, “Preparation of Self-Healing Protective Films on a Zinc Electrode Treated in a Cerium(III) Nitrate Solution and Modified with Sodium Phosphate and Cerium(III) Nitrate,” Corrosion Science, Vol. 46, No. 6, 2004, pp. 1565-1579.
 X. H. To, N. Pebere, N. Pelaprat, B. Boutevin and Y. Hervaud, “A Corrosion-Protective Film Formed on a Carbon Steel by an Organic Phosphonate,” Corrosion Science, Vol. 39, No. 10-11, 1997, pp. 1925-1934.
 H. Amar, T. Braisaz, D. Villemin and B. Moreau, “Thiomorpho-lin-4-Ylmethyl-Phosphonic Acid and Morpholin-4-Methyl-Phosphonic acid as Corrosion Inhibitors for Carbon Steel in Natural Seawater,” Materials Chemistry and Physics, Vol. 110, No. 1, 2008, pp. 1-6.
 R. O. Carter, C. A. Gierczak and R. A. Dickie, “The Chemical Interaction of Organic Materials with Metal Substrates. Part II: FT-IR Studies of Organic Phosphate Films on Steel,” Applied Spectroscopy, Vol. 40, No. 5, 1986, pp. 649-655. doi.org/10.1366/0003702864508656
 I. Sekine and Y. Hirakawa, “Effect of 1-Hydroxyethylidene-1,1-Diphosphonic Acid on the Corrosion of SS 41 Steel in 0.3% Sodium Chloride Solution,” Corrosion, Vol. 42, No. 5, 1986, pp. 272-277. doi.org/10.5006/1.3584904
 G. Gunasekaran, N. Palaniswamy, B. V. A. Rao and V. S. Muralidharan, “Synergistic Inhibition in Low Chloride Media,” Electrochimica Acta, Vol. 42, No. 9, 1997, pp. 1427-1434. doi.org/10.1016/S0013-4686(96)00366-0
 S. Yu and G. M. Chow, “Carboxyl Group (-CO2H) Functionalized Ferromagnetic Iron Oxide Nanoparticles for Potential Bio-Applications,” Journal of Materials Chemistry, Vol. 14, 2004, pp. 2781-2786.
 L. J. Bellamy, “Advances in Infrared Group Frequencies,” Chaucer Press Ltd., Auckland, 1968.
 J-G. Mao and A. Clearfield, “Metal Carboxylate-Phosphonate Hybrid Layered Compounds: Synthesis and Single Crystal Structures of Novel Divalent Metal Complexes with N-(Phosphonomethyl)Iminodiacetic Acid,” Inorganic Chemistry, Vol. 41, No. 9, 2002, pp. 2319-2324. doi.org/10.1021/ic011094w
 Y. I. Kuznetsov, Proceedings of the European Corrosion Congress (EUROCORR 2003), Budapest, 2003, p. 320.
 A. J. Freedman, “Cooling Water Technology in the 1980s,” Materials Performance, Vol 23, No. 11, 1984, pp. 9-16.
 V. Deluchat, J-C. Bollinger, B. Serpaud and C. Caullet, “Divalent Cations Speciation with Three Phosphonate Ligands in the pH-Range of Natural Waters,” Talanta, Vol. 44, No. 5, 1997, pp. 897-907.