Experimental And Computational Chemistry Simulation Studies On The Corrosion Inhibition Potentials Of Some Amino Acids

Experimental And Computational Chemistry Simulation Studies On The Corrosion Inhibition Potentials Of Some Amino Acids.

ABSTRACT

Inhibition and adsorption potentials of cysteine, glycine, leucine and alanine have been investigated using experimental and quantum chemical approaches.

The experimental study was carried out using gravimetric, gasometric, thermometric and FTIR methods of monitoring corrosion while the quantum chemical study was carried out using semi- empirical and ab-initio methods.

The results obtained reveal that various concentrations of the amino acids inhibited the corrosion of mild steel in solutions of hcl through the mechanism of physiosorption with activation energy less than 80kjmol^-1.

The inhibition potentials of the inhibitors decreased in the order, cysteine >leucine> alanine > glycine and their adsorption was found to be exothermic, spontaneous and fitted the Langmuir adsorption model.

Computational chemistry results obtained revealed excellent correlations between quantum chemical parameters (calculated for gas and aqueous phases PM6, PM3, AM1, RM1 and MNDO Hamiltonians) and experimental inhibition efficiencies. Correlations between the experimental and theoretical inhibition efficiencies were also excellent.

Application of condensed Fukui and softness functions, as well as relative nucleophilicity/electrophilicity (calculated for B3LYP(6-31G) and MP2(STO- 5G) paturbations), showed that the sites for electrophilic attack are on the amine bonds (N2-C3) of the amino acids while the sites for nucleophilic attack are on the C-3 atoms of the amino acids.

The HOMO and LUMO diagrams of the amino acids as well as the electron density diagrams have also been used to support the information obtained from condensed Fukui function.

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INTRODUCTION

The great expanded industrial applications of mild steel based on their properties have been recognized by many researchers (Eddy, 2008).

However, despite its importance, the problem associated with corrosion, especially pitting corrosion still remains a cause of concern to all and sundry. Huge losses of natural and artificial resources have been noted annually all over the globe as a result of corrosion.

In the petroleum and gas industries, more than half of the reported failures of pipelines are caused by corrosion and subsequent rupture of the pipe wall.

For, example, between 2002 and 2004, the Nigerian National Petroleum Corporation (NNPC) reported 162 cases of failure due to corrosion (Ajayi, 2003; Eddy, 2008) resulting in large losses of products, environmental pollution and ecological disaster.

Corrosion of metals has been a major industrial problem that has attracted much attention and investigations (Abiola et al., 2007; Arora et al., 2007. Ashassi-Sorkhabi et al., 2005a,2004;Barouni et al., 2008;Clark and Varney, 1987; Eddy, 2009a Kumar, 2008;

Muralidharan et al., 2000; Umoren and Ebenso, 2007,2008; Umoren et al., 2008a,b, 2006a,b). Corrosion is one of the major only means through which metals deteriorate.

Most metals corrode when they are in contact with aggressive medium such as moisture in the air, either in acids, bases, salts, oils, aggressive metals polishes, and liquid chemicals. Metals will also corrode when they are exposed to gaseous materials such as formaldehyde, acid vapour, and sulphur containing gases.

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REFERENCES

Abdallah, M. (2004a). Guar gum as corrosion inhibitor for carbon steel in sulphuric acid solutions. Portugaliae Electrochimica Acta, 22:161-175.
Abdallah, M. (2004b). Antibacterial drugs as corrosion inhibitors for aluminium in HCl solution. Corrosion Science,46: 1981-1996.
Abiola K.O., Oforka, N. C, Ebenso, E.E. and Nwinuka, N.M. (2007). Ecofriendly corrosion inhibitors: Inhibitive action of Delonix regia extract for the corrosion of aluminium in acidic medium. Anti-Corrosion Methods and Materials,54(4): 219- 224.
Acharya, S. and Upadhyay, S.N. (2004). The inhibition of corrosion of mild steel by some flouroquinolones in sodiumchloride solution. Transaction of the Indian Institute of Metals,57(3):297-306.
Affrossman, S.,Daviot J.,Holmes D,Pethrick R.A. andWilson, M. (2001). Molecular design for inhibition of titanium corrosion in resist cleaner systems. Corrosion Science,43 :939–950.
Ajayi, E.O. (2003). Predictive model for evaluating corrosion rate of mild steel in six environments. LAUTECH, Journal of Engineering and Technology,1:75-81.

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