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Electrochemical and Quantum Chemical Investigation on Adsorption of Nifedipine as Corrosion Inhibitor at API 5L X-52 Steel / HCl Acid Interface

Ikpi M. E., Abeng F. E.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

125--131

EN

Nifedipine, a pyridine derivative was investigated as corrosion inhibitor for API 5L X-52 steel in 2 M HCl solution by potentiodynamic polarization, electrochemical impedance spectroscopy and quantum chemical calculations. Statistical tools were used to compare results of the experimental methods. The results showed that nifedipine is capable of inhibiting the corrosion of API 5L X-52 steel in 2 M HCl solution. Potentiodynamic polarization results reveal that nifedipine functions as a mixed-type inhibitor and presents an inhibition efficiency of about 78% at 500 ppm. Impedance data reveal an increasing charge transfer resistance with increasing inhibitor concentration and also shows comparable inhibition efficiency of about 89-94% at 500 ppm. Thermodynamic parameters imply that nifedipine is adsorbed on the steel surface by a physiochemical process and obeys Langmuir adsorption isotherm. The calculated molecular properties namely the highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy, chemical hardness, energy gap, dipole moment, electronegativity and global nucleophilicity index all show a positive relationship to the observed corrosion inhibition efficiency.

2

Corrosion Inhibition of API 5L X52 Carbon Steel by 1-Ethyl-3-methylimidazolium-methanesulphonate and 1-Ethyl-3-methylimidazolium Acetate Ionic Liquids in Hydrochloric Acid

Ikpi Magdalene Edet, Obono Okama Ebri

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

295--304

EN

The corrosion inhibition behaviour of 1-Ethyl-3-methylimidazolium-methanesulphonate (EMIM[MS]) and 1-Ethyl-3-methylimidazolium acetate (EMIM[Ac]) on API 5LX-52 carbon steel in 2 M HCl was investigated using weight loss, potentiodynamic polarization and electrochemical impedance methods. The corrosion rates of carbon steel decreased in the presence of these ionic liquids. The inhibition efficiencies of the compounds increased with concentration and showed a marginal decrease with a 10°C increase in temperature. Polarization studies showed the compounds to be mixed type inhibitors with stronger anodic character. The adsorption mechanism of both compounds on the metal surface was via physical adsorption and the process obeyed the El-Awardy kinetic-thermodynamic model. The associated activation energy of corrosion and other thermodynamic parameters were calculated to elaborate on the thermodynamics and mechanism of the corrosion inhibition process. EMIM[MS] was found to inhibit the corrosion of carbon steel better than EMIM[Ac] and is attributed to the presence of the highly electronegative sulphur atom in its structure and its larger molecular size.

3

Problems with corrosion protection steel stacks in flue gas desulphurization systems

Krakowiak S., Żuchowski P.

Ochrona przed Korozją

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2013

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nr 3

94--96

EN

This paper presents problems associated with corrosion of steel stacks and changes in philosophy of corrosion protection when implemented into flue gas desulphurization systems. In-situ tests were taken by means of electrochemical impedance spectroscopy at a stack which discharges flue gas before wet lime/limestone desulphurization. A very rapid soaking of spherical infill vinylester coating with electrolyte has been observed. Based on the Brasher - Kingsbury equation and data obtained from impedance spectra water content in the tested coating has been calculated.

PL

Przedstawiono podstawowe problemy związane z korozją kominów stalowych oraz zmiany w filozofii zabezpieczenia ich przed korozją, gdy system zawiera instalację odsiarczania spalin. Wykonano badania terenowe metodą elektrochemicznej spektroskopii impedancyjnej w kominie odprowadzającym gazy po odsiarczaniu metodą mokrą wapniakowo-wapienną. Stwierdzono bardzo szybkie nasiąkanie elektrolitem powłoki winyloestrowej z wypełnieniem o kształcie kulistym. Na podstawie równania Brashera-Kingsbury i wyznaczonych na podstawie uzyskanych widm impedancyjnych obliczono zawartość wody w badanej powłoce.

4

Influence of Chemisorption o Sulfite Ions on Electroreduction of Gold(I)-Sulfite Complexes

Baltrunas G., Valiuniene A., Valiunas R.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 12

1819-1831

EN

Analysis of voltammograms, chronoamperograms and electrochemical impedance spectra (0.05÷4000 Hz) indicate a slow stage of chemisorption of sulfite ions that reduces an active surface of gold electrode, and significantly influences a parallel stage of charge transfer of gold(I)-sulfite complexes. The proposed equivalent circuit representing electrochemical process well fits to experimental dependencies of real and imaginary parts of impedance on frequency. Values of elements of equivalent circuit at different potentials of gold electrode (0.1÷-0.5 V) were calculated. Cathodic voltammogram simulated by using the dependencies of elements of equivalent circuit on electrode potential rather well represents experimentally obtained voltammograms.