Acid corrosion inhibition of ferrous and non-ferrous metal by nature friendly Ethoxycarbonylmethyltriphenylphosphonium Bromide (ECMTPB): Experimental and MD simulation evaluation

https://doi.org/10.1016/j.molliq.2020.113705Get rights and content

Highlights

  • Phosphonium ionic salts are reported as corrosion inhibitors.

  • Electrochemical, theoretical and surface morphological techniques were used.

  • The results were supported by MD, SEM, AFM and QC Calculations.

Abstract

Electrochemical techniques, using galvanostatic polarization and electrochemical impedance spectroscopy (EIS) as experimental; Quantum Chemical (QC) calculation and Molecular dynamics (MD) simulation as theoretical methods and Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) as surface morphological studies have been accomplished to evaluate the corrosive inhibitive property of Ethoxycarbonylmethyl Triphenylphosphonium Bromide (ECMTPB) for Mild Steel (MS) in 0.5 M H2SO4 and Aluminium (Al) in 0.5 M HCl solutions, respectively. The protective rate of both the materials increased with increase in the concentration of 10−5 M to 10−2 M of ECMTPB as well as with room temperature. The Nyquist plot of impedance expressed mainly as a depressed capacitive loop with different concentrations. The mechanism of inhibition of corrosion of MS and Al in acidic medium follows Langmuir adsorption isotherm and inhibitor is being chemisorbed predominantly on the metal surface. The images found from Surface Morphological Studies Viz., SEM with EDX supplements the results obtained from the experimental and theoretical studies. The properties of single ECMTPB molecule from QM and the interaction energies between inhibitor and metals from classical simulations indicate the possible mechanism of preventing corrosion of inhibitor.

Introduction

Metallic corrosion has continued to receive awareness in the whole world because metallic deterioration is an extensively engineering and economic setback [[1], [2], [3], [4]]. Madhusudan Goyal et al., published a review on organic corrosion inhibitors for industrial cleaning of ferrous and non-ferrous metals in acidic solutions: A review [5]. The research of Corrosion on aluminium and iron/MS has received generous interest by researchers in the various corrosive environments due to their industrial applications and technological importance. Aluminium metal is next to iron/MS in conditions of consumption and production. Iron/MS and aluminium get applications, essentially in electronic devices, aviation, automobiles, containers and household appliances. Reported literature reveals that extensive studies are conducted on corrosion behavior of aluminium (Al) in hydrochloric acid (HCl) and mild steel (MS) in sulfuric acid (H2SO4) medium [[6], [7], [8], [9], [10]]. However, researchers are continual in seeking better and more capable methods of combating the corrosion of metals. The best method is to isolate corrosion on metals from corrosive media by the use of corrosion inhibitors.

Phosphorus-containing aromatic heterocyclic organic compounds have been found to be effective corrosion inhibitors [11,12]. M.A. Quraishi co-worker have also reported the effectiveness of ionic liquids (ILs) as green inhibitors for metals and alloys corrosion [13] Quaternary phosphonium compounds is another a class of ionic salts/liquids which represent a promising alternative for inventing of “eco-friendly” corrosion inhibitors. Many researchers worked on the inhibition effect of nature friendly inhibitors like quaternary phosphonium compounds on corrosion of metal in acidic environment because these are cost-effective, biodegradable, non-toxic, produced with high purity and completely soluble in aqueous media [14,15]. In this continuation, Madhusudan and his co-worker et al. investigated on the anti-corrosion properties of eco-friendly phosphonium compounds such as 2-aminobenzyl triphenylphosphonium bromide (ABTPB) [16], MethoxycarbonylmethylTriphenylphonium bromide (MCMTPPB) [17], TetrabutylPhosphonium hydroxide (TBPH) [18] for the corrosion of metal in acidic environment. These compounds fulfill the central requirements of being a good inhibitor of corrosion for metals. For example, the presence of the heteroatom, here phosphorus; the presence of π-e in conjugation; and the presence of different groups which can attach themselves to the metal, will all result in very high inhibition. These groups are observed as the reaction center that stabilizes the adsorption process and block the corrosive spots on the surface of metal, thereby falling the rate of corrosion. They exhibit surface active properties through the hydrophobic and hydrophilic groups attached to the central atom to form yield. They are also thermally stable and therefore, these are suitable for reactions carried out even at higher temperatures up to 400 K. These compounds can be easily applied to the metal surface by immersion or by incorporating them in polymer coatings. These were into applying not only due to their protective potency but also attributable to their safety. There is a unique emphasis on natural compounds which are non-toxic and ecologically friendly. Keeping this in mind it was decided to explore new compound belonging to phosphonium class as nature-friendly corrosion inhibitor.

The present work assure the inhibiting behavior of the Ethoxycarbonylmethyltriphenylphosphonium Bromide (ECMTPB) on MS in 0.5 M sulfuric acid and Al in 0.5 M HCl solution using electrochemical measurements and surface morphological (SEM-EDX) studies. Thermodynamic parameters were analysis to reveal the nature (Physio-chemio adsorption) of ECMTPB inhibitor on the surface. The effects of this inhibitor have been correlated to its molecular structure, and electronic properties are being calculated theoretically. The outcomes of quantum chemical (QC) calculations and Molecular dynamics (MD) simulations are good in agreement with the result acquired from experimental electrochemical and surface morphological studies.

Section snippets

Inhibitor used

The nature friendly, Organic compound Ethoxycarbonylmethyltriphenylphosphonium Bromide (ECMTPPB) is preferred as the proficient corrosion inhibitor for this current research and obtained from the Alfa Aesar chemicals, pro lab marketing limited, New Delhi, India. Using inhibitor is biodegradable, non-toxic, and eco-friendly compounds prepared with high purity at cheap expenditure. The inhibitor ECMTPB has the following physical properties, such as solid in the state, stable in water, Molecular

Galvanostatic polarization studies (GPS)

The mechanistic studies of corrosion inhibition of mild steel (MS) and aluminium (Al) surface in 0.5 M sulfuric acid and 0.5 M hydrochloric acid using galvanostatic polarization studies were done using EthoxycarbonylmethylTriphenylPhosphonium Bromide (ECMTPB) at four temperatures – 298 K to 328 K at 10 K difference, cathodic and anodic polarization curves were examined in Fig. 2(a–d), respectively.

The inhibition efficiency (IEGPS %) was calculated from Tafel plots accordance with the expression

Conclusion

  • Based on the electrochemical test, polarization curves proved that the triphenylphosphonium derivative ECMTPB was mixed-type inhibitor with cathodic predominately in acidic medium as was evident from the insignificant shift of OCP values in cathodic direction (Al > MS).

  • Aluminium under goes less corrosion in HCl when compared with Mild Steel in H2SO4 in the presence of ECMTPB because aluminium did not corrode easily due to its surface is protected by a layer of aluminium oxide at higher

CRediT authorship contribution statement

Madhusudan Goyal: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Hemlata Vashist: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing -

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

Authors are grateful to the University of Delhi, University Grants Commission (UGC), and SERB (DST) India for granting funding to carry out their research work. The first author, Dr. Madhusudan Goyal, is grateful to the advisor Prof. Gurmeet Singh, Department of Chemistry, University of Delhi for enlightening me the first glance of research and also wholeheartedly thankful to my parents Smt. Sarla and Sh. Naresh Goyal and my wife Dr. Renu Goyal for being a constant source of moral support and

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