On the corrosion inhibition of low carbon steel in concentrated sulphuric acid solutions. Part I: Chemical and electrochemical (AC and DC) studies

Abstract The influence of the concentration of adenine (AD), as a safe inhibitor, on the corrosion of low carbon steel (LCS) in aerated 4.0 M H 2 SO 4 solutions was studied. The investigations involved weight loss, potentiodynamic polarization, impedance and electrochemical frequency modulation (EFM) methods. Variations of open-circuit potential (OCP) as a function of time till steady-state potentials were also studied. Measurements were conducted under the influence of various experimental conditions complemented with ex situ EDX examinations of the electrode surface. By using EFM measurements, corrosion current density was determined without prior knowledge of Tafel slopes. Results obtained revealed that together with iodide ion, AD is an effective corrosion inhibitor for LCS corrosion in H 2 SO 4 solutions. Synergism between iodide ion and AD was proposed. Potentiodynamic polarization studies showed that AD alone and the mixture of AD and iodide ions act as mixed-type inhibitors for the corrosion of LCS in 4.0 M H 2 SO 4 solution. The inhibition mechanism involves the electrostatic adsorption of protonated AD molecules on the LCS surface charged with a negative layer of chemisorbed I − ions. An adherent layer of inhibitor is postulated to account for the protective effect. EDX examinations of the electrode surface confirmed the existence of such adherent layer on the electrode surface. The inhibition efficiency increases with increase in the concentration of AD and immersion time. The potential of zero charge (PZC) of the LCS electrode was determined in 4.0 M H 2 SO 4 solutions in the absence and presence of 0.001 M KI, and the mechanism of adsorption was discussed. The results obtained from chemical and electrochemical measurements were in good agreement.

[1]  S. Bilgiç,et al.  Effect of amino acids on corrosion of cobalt in H2SO4 , 1993 .

[2]  C. J. Drayton,et al.  Comprehensive heterocyclic chemistry : the structure, reactions, synthesis, and uses of heterocyclic compounds , 1984 .

[3]  G. Mu,et al.  The adsorption and corrosion inhibition of anion surfactants on aluminium surface in hydrochloric acid , 1999 .

[4]  K. L. Tan,et al.  Electrochemical impedance and X-ray photoelectron spectroscopic studies of the inhibition of mild steel corrosion in acids by cyclohexylamine , 1997 .

[5]  S. Martinez,et al.  Ferric-Tannate Formation and Anticorrosive Properties of Mimosa Tannin in Acidic Solutions , 1999 .

[6]  F. Mansfeld,et al.  An evaluation of the electrochemical frequency modulation (EFM) technique , 2006 .

[7]  M. Scendo.  Corrosion inhibition of copper by purine or adenine in sulphate solutions , 2007 .

[8]  M. Scendo.  The effect of purine on the corrosion of copper in chloride solutions , 2007 .

[9]  S. Bilgiç,et al.  The effect of amino acids on the corrosion of nickel in H2SO4 , 1992 .

[10]  F. M. Starr.  Equivalent circuits , 1932, Electrical Engineering.

[11]  Francesca Guidi,et al.  Tryptamine as a green iron corrosion inhibitor in 0.5 M deaerated sulphuric acid , 2004 .

[12]  K. F. Khaled,et al.  Electrochemical frequency modulation as a new technique for monitoring corrosion inhibition of iron in acid media by new thiourea derivative , 2006 .

[13]  G. Schmitt,et al.  Investigations on structural and electronic effects in acid inhibitors by AC impedance , 1985 .

[14]  J. Pan,et al.  Tafel slopes used in monitoring of copper corrosion in a bentonite/ groundwater environment , 2005 .

[15]  H. Flitt,et al.  A guide to polarisation curve interpretation: deconstruction of experimental curves typical of the Fe/H2O/H+/O2 corrosion system , 2005 .

[16]  N. Hackerman,et al.  Inhibition Mechanism of Medium‐Sized Polymethyleneimine , 1969 .

[17]  Denny A. Jones.  Principles and prevention of corrosion , 1991 .

[18]  M. Amin,et al.  Corrosion inhibition study of pure Al and some of its alloys in 1.0 M HCl solution by impedance technique , 2004 .

[19]  M. Amin,et al.  The corrosion inhibition study of sodium dodecyl benzene sulphonate to aluminium and its alloys in 1.0 M HCl solution , 2003 .

[20]  W. Bogaerts,et al.  Instantaneous Corrosion Rate Measurement with Small-Amplitude Potential Intermodulation Techniques , 1996 .

[21]  A. Fouda,et al.  Aminopyrimidine derivatives as inhibitors for corrosion of 1018 carbon steel in nitric acid solution , 2006 .

[22]  V. V. Batrakov,et al.  Adsorption of Organic Compounds on Electrodes , 1971 .

[23]  A. Łukomska,et al.  Potential of zero charge of monocrystalline copper electrodes in perchlorate solutions , 2004 .

[24]  N. Hackerman.  The theory and practice of corrosion and its control in industry , 1987 .

[25]  F. Mansfeld,et al.  Determination of corrosion rates by electrochemical DC and AC methods , 1981 .

[26]  W. G. Proud,et al.  Electrochemical studies of copper, copper-aluminium and copper-aluminium-silver alloys: Impedance results in 0.5M NaCl , 1995 .

[27]  H. Hassan,et al.  Corrosion inhibition of aluminum by 1,1(lauryl amido)propyl ammonium chloride in HCl solution , 2001 .

[28]  Walter Bogaerts,et al.  Electrochemical Frequency Modulation: A New Electrochemical Technique for Online Corrosion Monitoring , 2001 .

[29]  L. Gao,et al.  Synergistic effect of 2-mercapto benzimidazole and KI on copper corrosion inhibition in aerated sulfuric acid solution , 2003 .

[30]  Giuseppe Quartarone,et al.  Inhibition of copper corrosion by isatin in aerated 0.5 M H2SO4 , 2003 .

[31]  O. R. Mattos,et al.  Mass‐Transport Study for the Electrodissolution of Copper in 1M Hydrochloric Acid Solution by Impedance , 1993 .

[32]  M. Amin,et al.  Corrosion and corrosion inhibition of Al and some alloys in sulphate solutions containing halide ions investigated by an impedance technique , 2002 .

[33]  H. Nishihara,et al.  Permeability of alkanethiol self-assembled monolayers adsorbed on copper electrodes to molecular oxygen dissolved in 0.5 M Na2So4 solution , 1996 .

[34]  M. Amin.  Weight loss, polarization, electrochemical impedance spectroscopy, SEM and EDX studies of the corrosion inhibition of copper in aerated NaCl solutions , 2006 .

[35]  S. S. A. El-rehim,et al.  The inhibition of low carbon steel corrosion in hydrochloric acid solutions by succinic acid: Part I. Weight loss, polarization, EIS, PZC, EDX and SEM studies , 2007 .

[36]  A. Din,et al.  Corrosion inhibition by molybdate/polymaliate mixtures , 1997 .

[37]  B. Boukamp.  A Nonlinear Least Squares Fit procedure for analysis of immittance data of electrochemical systems , 1986 .

[38]  G. Mu,et al.  The effect of neutral red on the corrosion inhibition of cold rolled steel in 1.0 M hydrochloric acid , 2003 .

[39]  H. Flitt,et al.  Evaluation of corrosion rate from polarisation curves not exhibiting a Tafel region , 2005 .

[40]  M. Musiani,et al.  Electrochemical behaviour of copper in neutral aerated chloride solution. I. Steady-state investigation , 1988 .

[41]  M. Scendo.  Inhibitive action of the purine and adenine for copper corrosion in sulphate solutions , 2007 .

[42]  Shenhao Chen,et al.  General Equivalent Circuits for Faradaic Electrode Processes under Electrochemical Reaction Control , 1999 .

[43]  G. Moretti,et al.  Tryptophan as copper corrosion inhibitor in 0.5 M aerated sulfuric acid , 2002 .

[44]  K. Siow,et al.  The synergistic effects of propargyl alcohol and potassium iodide on the inhibition of mild steel in 0.5 M sulfuric acid solution , 1999 .

[45]  Florian Mansfeld,et al.  Tafel slopes and corrosion rates obtained in the pre-Tafel region of polarization curves , 2005 .