Elsevier

Journal of Molecular Liquids

Volume 219, July 2016, Pages 647-660
Journal of Molecular Liquids

3-Amino alkylated indoles as corrosion inhibitors for mild steel in 1M HCl: Experimental and theoretical studies

https://doi.org/10.1016/j.molliq.2016.04.024Get rights and content

Highlights

  • The inhibitory effect of 3-amino alkylated indoles (AAIs) on mild steel was studied in 1M HCl.

  • Langmuir adsorption isotherm gave the best fit to the experimental data.

  • SEM and AFM results showed that presence of AAIs decreases the surface roughness.

  • The adsorption of AAIs is the mixed type of chemical and physical interactions.

  • Experimental results were supported by quantum chemical calculation and molecular dynamics simulations.

Abstract

The present study describes the influence of ring and ring size of three 3-amino alkylated indoles (AAIs) namely, N-((1H-indol-3-yl)(phenyl)methyl)-N-ethylethanamine (AAI-1), 3-(phenyl(pyrrolidin-1-yl)methyl)-1H-indole (AAI-2) and 3-(phenyl(piperidin-1-yl)methyl)-1H-indole (AAI-3) on mild steel corrosion in 1M HCl solution using gravimetric, electrochemical, surface morphology (SEM, AFM), quantum chemical calculations and molecular dynamics simulations methods. Both experimental and theoretical results showed that the 3-amino alkylated indoles with cyclic amino groups exhibit higher inhibition efficiency compared to the one with opened-chain amino group. The results further suggested that the inhibition efficiency increases with increasing ring size of the amino group such that the piperidine-containing (6-membered ring) 3-amino alkylated indole showed higher inhibition performance than the pyrrolidine-containing (five membered) 3-amino alkylated indole. Experimental results revealed that the inhibition efficiency increases with increasing concentration of the inhibitors. Maximum inhibition efficiencies of 94.34% for AAI-1, 96.08% for AAI-2 and 96.95% for AAI-3 were obtained at 0.862 mM concentration. EIS measurements showed that the studied compounds inhibit mild steel corrosion by adsorbing on the steel surface. Polarization studies revealed that the compounds are cathodic type inhibitors. The adsorption of the studied compounds obeyed the Langmuir adsorption isotherm. SEM and AFM surface morphology analyses also provided evidence of formation of adsorbed film of the AAIs on the steel surface. Theoretical parameters such as EHOMO and electronegativity derived from quantum chemical calculations as well as binding energy derived from molecular dynamics simulations studies adequately corroborate the trend of experimental inhibition efficiencies of the studied inhibitors.

Introduction

Acid solutions are commonly used for pickling and also for the removal of rust and scales in petroleum industries [1], [2], [3], [4]. The use of acid solutions for these industrial activities results in loss corrosion and eventually loss of metals. Addition of organic corrosion inhibitors, which are compounds that contain heteroatoms (e.g. N, O and S), double and triple bonds and aromatic rings has been identified as one of the most practical and economical ways of controlling metal corrosion [5], [6], [7], [8]. These compounds inhibit metallic corrosion by becoming adsorbate at metal/electrolyte interfaces in which polar functional groups such –NH2, –OH, − CN, − NO2 etc. and pi-electrons of the double and triple bonds and aromatic rings act as adsorption centers [9], [10], [11]. Adsorption of these compounds depends upon several factors including molecular weight, nature of substituents, solution temperature, nature of inhibitor and electrolytes etc. [12], [13]. However, most of the previously existing corrosion inhibitors are toxic and non-environmental friendly [14], [15]. The current strict measures on environmental regulations and increasing ecological awareness have shifted the attentions of corrosion control experts toward the development of efficient and environmentally benign corrosion inhibitors [16], [17], [18]. In this direction, multicomponent reactions (MCRs), which combine three or more substrates is one of the most relevant current approaches that are able to produce several bonds in one step [19], [20], [21], [22]. In addition, the MCRs have other several advantages including operational simplicity, facile automation and minimized waste generation, because of the reduction in the number of work-up, extraction and purification stages [19], [23]. In spite of the theory of famous ancient philosopher of Greece, namely Aristotle, the “No Coopora nisi Fluida” which means “No reaction takes place in absence of solvent”, in recent years organic synthesis in solid phase (solvent free condition) attracted great deal of attraction due to their reduce pollution, low costs, and simplicity in process and handling [24]. Certainly, in several cases, solvent free reactions takes place with high yield and selectivity than does their solution counterpart because of the more tight and regular arrangement of molecules in the crystal form [20], [25]. Furthermore, “green chemistry” emphasizes the optimization of synthetic methodologies to reduce environmental pollution, cost and tedious work-ups. This new challenge has led to a growing interest in the field of organic synthesis using catalyst derived from natural resources [26], [27]. In asymmetric organocatalysis, consumption of l-proline provides the means of upholding the essential principles of green chemistry as it is directly isolated from natural biological sources without use of any hazardous chemical and/or solvents such as DMSO, DMF and other chlorinated solvents [28]. Literature survey reveals that indole and its derivatives act as efficient metallic corrosion in different electrolytic media [29], [30], [31], [32], [33]. These compounds inhibit metallic corrosion by becoming adsorbate at the metal/electrolyte interface in which indole moiety acts as adsorption center.

In the present study, the effect of the type of amine (opened chain or cyclic) as well as ring size of cyclic amine on the corrosion inhibition efficiency of three newly synthesized 3-amino alkylated indoles (AAIs) namely, N-((1H-indol-3-yl)(phenyl)methyl)-N-ethylethanamine (AAI-1), 3-(phenyl(pyrrolidin-1-yl)methyl)-1H-indole (AAI-2) and 3-(phenyl(piperidin-1-yl)methyl)-1H-indole (AAI-3) on mild steel corrosion in 1M HCl solution is being investigated for the first time. The corrosion inhibition performances of the three newly synthesized AAIs were determined using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. Quantum chemical calculations and molecular dynamics simulations studies were also carried out to provide more insights into the theoretical explanations of the inhibition activities of the studied compounds.

Section snippets

Electrode and reagents

The mild steel specimens for weight loss, electrochemical and surface measurements were cut form commercially available mild steel sheet having chemical composition (wt%): C (0.076), Mn (0.192), P (0.012), Si (0.026), Cr (0.050), Al (0.023), and Fe (balance). The exposed surface of the working electrodes were cleaned successively with emery papers of different grade (600, 800, 1000, and 1200), washed with deionized water, degreased with acetone, ultrasonically cleaned with ethanol and stored in

Effect of AAIs concentration

Table 2 represents the parameters derived from the weight loss experiments after 3 h immersion time in absence and presence different concentrations of the investigated inhibitors. It can be seen from the results that inhibition efficiency increases with increasing concentration of all inhibitors and maximum values of inhibition efficiencies of 94.34% for AAI-1, 96.08% for AAI-2 and 96.95% for AAI-3 were obtained at 0.862 mM concentration. However, careful examination of the results depicted in

Conclusion

Three new 3-amino alkylated indoles (AAIs) namely, N-((1H-indol-3-yl)(phenyl)methyl)-N-ethylethanamine (AAI-1), 3-(phenyl(pyrrolidin-1-yl)methyl)-1H-indole (AAI-2) and 3-(phenyl(piperidin-1-yl)methyl)-1H-indole (AAI-3) have been synthesized and investigated for their inhibition performances on mild steel corrosion in 1M HCl solution. The results of both gravimetric and electrochemical experiments showed that all the three compounds inhibit mild steel corrosion in 1M HCl solution and the

Acknowledgment

Chandrabhan Verma, gratefully acknowledges Ministry of Human Resource Development (MHRD), New Delhi (India) for providing financial assistance and facilitation for present study.

References (77)

  • K. Zhang et al.

    Corros. Sci.

    (2015)
  • S.M. Shaban et al.

    J. Mol. Liq.

    (2015)
  • A.A. Farag et al.

    J. Ind. Eng. Chem.

    (2015)
  • C. Verma et al.

    J. Mol. Liq.

    (2015)
  • C. Verma et al.

    J. Mol. Liq.

    (2015)
  • F.S. de Souza et al.

    Corros. Sci.

    (2009)
  • O.K. Abiola et al.

    Corros. Sci.

    (2009)
  • A.A. El-Shafei et al.

    Corros. Sci.

    (2004)
  • K.F. Khaled

    Mater. Chem. Phys.

    (2008)
  • P. Lowmunkhong et al.

    Corros. Sci.

    (2010)
  • M. Lebrini et al.

    Corros. Sci.

    (2010)
  • G. Quartarone et al.

    Corros. Sci.

    (2008)
  • N.K. Gupta et al.

    J. Mol. Liq.

    (2016)
  • J.P. Zeng et al.

    Compt. Theo. Chem.

    (2011)
  • I.B. Obot et al.

    Corros. Sci.

    (2014)
  • E.E. Ebenso et al.

    Mater. Chem. Phys.

    (1999)
  • A.M. Al-Sabagh et al.

    Egypt. J. Pet.

    (2012)
  • J. Cai et al.

    Int. J. Electrochem. Sci.

    (2012)
  • C. Verma et al.

    J. Mol. Liq.

    (2015)
  • E.A. Noor et al.

    Al-Moubaraki

    Mater. Chem. Phys.

    (2008)
  • R. Solmaz

    Corros. Sci.

    (2014)
  • R. Solmaz

    Corros. Sci.

    (2014)
  • S. Ghareba et al.

    Corros. Sci.

    (2010)
  • A. Hamdy et al.

    Egypt. J. Pet.

    (2013)
  • C.M. Goulart et al.

    Corros. Sci.

    (2013)
  • M.A. Amin et al.

    Corros. Sci.

    (2011)
  • M.A. Amin et al.

    Corros. Sci.

    (2011)
  • F. Bentiss et al.

    Corros. Sci.

    (2005)
  • J. Zhao et al.

    Corros. Sci.

    (2015)
  • F. Bentiss et al.

    Mater. Chem. Phys.

    (2004)
  • P. Roy et al.

    Corros. Sci.

    (2014)
  • M. Ozcan et al.

    Appl. Surf. Sci.

    (2004)
  • R. Solmaz

    Corros. Sci.

    (2010)
  • M. El Achouri et al.

    Prog. Org. Coat.

    (2001)
  • C. Verma et al.

    J. Taiwan. Ins.Chem. Eng.

    (2015)
  • C. Verma et al.

    J. Mol. Liq.

    (2015)
  • L. Herrag et al.

    Corros. Sci.

    (2010)
  • B. Xu et al.

    Corros. Sci.

    (2014)
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