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Corrosion Inhibition and Adsorption Behavior of Punica granatum Extract on Mild Steel in Acidic Environments: Experimental and Theoretical Studies Maduabuchi A. Chidiebere,† Cynthia E. Ogukwe,† Kanayo L. Oguzie,‡ Chukwuemeka N. Eneh,† and Emeka E. Oguzie*,† †
Electrochemistry and Materials Science Research Laboratory Department of Chemistry and ‡Department of Environmental Technology, Federal University of Technology Owerri, PMB 1526, Owerri, Nigeria ABSTRACT: The adsorption and corrosion inhibiting effect of aqueous extracts of Punica granatum (PNG) on mild steel in 1 M HCl and 0.5 M H2SO4 at 30 ( 1 °C was investigated using gravimetric, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques. The experimental findings revealed that PNG inhibited the corrosion reaction in both acid environments. Impedance results indicate that the extract organic matter was adsorbed on the metal/solution interface, while polarization data show that the extract behaved mostly as a mixed-type inhibitor. A theoretical study of the adsorption behavior of some of the components of the crude extracts was carried out in the framework of the density functional theory (DFT).
acid.13 Okafor et al.14 reported the inhibitive action of ethanol extracts of Phylantus amarus on the corrosion of mild steel in H2SO4 solutions. Extracts from Aloe vera,15 Justicia genderussa,16 Murraya koenigii leaves,17 black pepper,18 Artemisia pallens,19 Ananas comosus L.,20 Raphia hookeri,21 henna,22 and fruit peel aqueous extracts23 as well as tapioca starch24 have all been reported to inhibit metal corrosion in different environments. The corrosion inhibiting efficacy of these extracts is normally ascribed to the presence, in their composition, of complex organic (phytochemical) species such as tannins, alkaloids and nitrogen bases, carbohydrates, and proteins as well as their acid hydrolysis products. Again, in spite of the availability and vast varieties of plant biomass, only a relatively few have been thoroughly investigated as corrosion inhibitors and the inhibition mechanisms are as well yet to be properly understood. One reason for this state of affairs is the complicated chemical composition of biomass extracts, such that successful assignment of any observed inhibitive effect to adsorption of any particular constituent or even determination of the contributions of the different extract constituents to the overall inhibiting effect continues to pose a considerable experimental challenge. In recent times, density functional theory (DFT) based quantum chemical computations have proven to be very useful in elucidating the electronic structures and reactivity of a wide range of organic molecules. Thus, it has become common practice to incorporate quantum chemical calculations in the study of organic corrosion inhibitors.2529 Recently, we have attempted to extend the application of DFT techniques to the assessment of the adsorption behavior of selected constituents of biomass extracts, especially those with molecular structures similar to those of conventional corrosion inhibitors.30 This computational
1. INTRODUCTION Acid solutions are often used in drilling operations in oil and gas explxoration, as well as for cleaning, descaling, and pickling of steel structures, processes which are normally accompanied by considerable dissolution of the metal. A useful method to protect metals and alloys deployed in service in such aggressive environments against corrosion is addition of species to the solution in contact with surface in order to inhibit the corrosion reaction and reduce the corrosion rate. A number of organic compounds are known to be applicable as corrosion inhibitors for steel in acidic environments.18 Such compounds typically contain nitrogen, oxygen, or sulfur in a conjugated system and function via adsorption of the molecules on the metal surface, creating a barrier to corrodent attack. Adsorption bond strength is dependent on the nature of the metal and corrodent, inhibitor structure, and concentration as well as temperature. Despite the wide range of available organic compounds, the final choice of the appropriate inhibitor for a particular application is restricted by several factors, including increased environmental awareness and the need to promote environmentally friendly processes, coupled with the specificity of action of most acid inhibitors, which often necessitates use of combinations of additives to provide the multiple services needed for effective corrosion inhibition. Consequently there exists the need to develop a new class of corrosion inhibitors with low toxicity and good efficiency. Natural products of plant origin are inexpensive, eco-friendly, and renewable sources of materials. The extracts from their leaves, barks, seeds, fruits, and roots comprise mixtures of organic compounds containing nitrogen, sulfur, and oxygen atoms, and some have been shown to function as effective inhibitors of metal corrosion in different aggressive environments. Oguzie reported the inhibitive effect of some plant extracts, such as Occimum viridis,9 Telferia occidentalis,10 Azadirachta indica,11 and Hibiscus sabdariffa,12 on the acid corrosion of mild steel. Gunasekaran and Chauhan in their study observed that extracts from Zenthoxylum alatum plant inhibited the corrosion of mild steel in phosphoric r 2011 American Chemical Society
Received: August 29, 2011 Accepted: December 19, 2011 Revised: December 16, 2011 Published: December 19, 2011 668
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approach makes it possible to predict how the respective constituents, on the basis of their individual adsorption energies, may contribute to the observed corrosion inhibiting effect. The present paper describes experimental and theoretical evaluation of the adsorption and corrosion inhibiting effect of aqueous extracts from seeds of Punica granatum (pomegranate) on the acid corrosion of mild steel.
2. EXPERIMENTAL SECTION 2.1. Materials Preparation. Tests were performed on mild steel specimens with weight percentage composition as follows: C, 0.05%; Mn, 0.6%; P, 0.36%; Si, 0.3%; balance Fe. The aggressive acid environments were respectively 1 M HCl and 0.5 M H2SO4 solutions. Stock solutions of the plant extract were prepared by refluxing weighed amounts of the dried and ground seeds of P. granatum (PNG) in ethanol for 3 h. The resulting solution was cooled and then triple filtered. The obtained filtrate had a dark blue color, due essentially to the presence of plant pigments. The amount of plant material extracted into solution was quantified by comparing the weight of the dried residue with the initial weight of the dried plant material before extraction. Inhibitor test solutions were prepared in the desired concentration range by diluting the stock extract with the aggressive solution. 2.2. Gravimetric Experiments. Gravimetric experiments were conducted on test coupons of dimensions 3 cm 3 cm 0.14 cm. These were abraded using SiC abrasive paper (up to 1000 grit), washed with distilled water, and dried in acetone and warm air. The precleaned and weighed coupons were suspended in beakers containing the test solutions using glass hooks and rods. Tests were conducted under total immersion conditions in 300 mL of the aerated and unstirred test solutions. To determine weight loss with respect to time, test coupons were retrieved at 24 h intervals progressively for 120 h, immersed in 20% NaOH solution containing 200 g/L zinc dust, scrubbed with a bristle brush, washed, dried, and reweighed. The weight loss was taken as the difference between the initial and final weights of the coupons. The results presented are means of triplicate determinations with standard deviation ranging from 0 to 0.0007. 2.3. Electrochemical Measurements. Test metal samples for electrochemical experiments were machined into cylindrical specimens and fixed in polytetrafluoroethylene (PTFE) rods by epoxy resin in such a way that only one surface of area 1 cm2 was left uncovered. The exposed surface was also cleaned as described above. Electrochemical experiments were conducted in a three-electrode corrosion cell using a VERSASTAT 400 complete dc voltammetry and corrosion system, with V3 Studio software. A platinum sheet was used as counter electrode, and a saturated calomel electrode (SCE) was used as reference electrode. The latter was connected via a Luggin’s capillary. Measurements were performed in aerated and unstirred solutions at the end of 1 h of immersion at 30 ( 1 °C. Impedance measurements were made at corrosion potentials (Ecorr) over a frequency range of 100 kHz0.1 Hz, with a signal amplitude perturbation of 5 mV. Potentiodynamic polarization studies were carried out in the potential range (250 mV versus corrosion potential at a scan rate of 0.333 mV s1. Each test was run in triplicate to verify the reproducibility of the data. 2.4. Quantum Chemical Calculations. All theoretical calculations were performed using the density functional theory (DFT)
Figure 1. Variation of weight loss with exposure time for mild steel corrosion in (a) 0.5 M H2SO4 and (b) 1 M HCl in the presence and absence of PNG at 30 °C.
electronic structure programs Forcite and DMol3 as contained in the Materials Studio 4.0 software (Accelrys, Inc.).
3. RESULTS AND DISCUSSION 3.1. Gravimetric Results. 3.1.1. Weight Loss and Corrosion Rate. The anodic dissolution of iron (Fe(s) f Fe2+(aq) + 2e),
coupled with the high solubility of the corrosion products, results in considerable weight loss for mild steel immersed in an acidic solution. Figure 1 illustrates the weight loss of the mild steel specimen as a function of time in 0.5 M H2SO4 (Figure 1a) and 1 M HCl (Figure 1b) without and with different concentrations of PNG. The inset in Figure 1a shows the actual trend of weight loss in uninhibited 0.5 M H2SO4 (which, in the larger plot, appears to remain constant at t > 24 h). The results indicate that the corrosion rate in all systems increased with exposure time and that PNG actually retarded mild steel corrosion at all concentrations in 1 M HCl and at concentrations greater than 50 mg/L in 0.5 M H2SO4. Low concentrations of PNG stimulate the corrosion process in 0.5 M H2SO4 for immersion times t > 24 h. Corrosion rates in 1 M HCl decreased steadily with PNG concentration from 25 mg/L up to an optimum value of 400 mg/L, whereas that in 0.5 M H2SO4 decreased steadily from 25 to 600 mg/L. 669
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Figure 2. Variation of inhibition efficiency with PNG concentration and immersion time in (a) 0.5 M H2SO4 and (b) 1 M HCl.
3.1.2. Inhibition Efficiency. Quantitative characterization of the inhibiting effect of PNG extract on the free corrosion of mild steel was carried out by an assessment of the inhibition efficiency (IE%) defined by ΔWinh 100 ð1Þ IE% ¼ 1 ΔWblank
Figure 3. Potentiodynamic polarization curves for mild steel in (a) 0.5 M H2SO4 and (b) 1 M HCl in the presence and absence of PNG extract.
ΔWinh and ΔWblank are the weight losses in inhibited and uninhibited corrodent, respectively. Parts a and b of Figure 2 show the variation of inhibition efficiency with PNG concentration and immersion time in 0.5 M H2SO4 and 1 M HCl, respectively. The negative values observed at low PNG concentrations ( 400 mg/L in 1 M HCl further confirms the waning influence of protonated species at high PNG extract concentrations. The trend of inhibition efficiency with immersion time can be related to the adsorbability of the extract organic matter on the metal surface. The high corrosion rates associated with increasing immersion time could promote desorption of adsorbed inhibitor species or restrict the adsorption process. Both effects will lead to gradual reduction in inhibition efficiency with increasing immersion time as observed for all PNG concentrations in 1 M HCl and at [PNG] < 600 mg/L in 0.5 M H2SO4. The adverse influence of increasing immersion time on inhibition efficiency waned progressively with increasing PNG concentration in 0.5 M H2SO4. This means that increasing the concentration of PNG in this environment gradually enhanced the adsorbability of the extract, possibly because certain constituents of the extract become available in sufficient amounts for
chemical interaction with the metal surface, thereby buffering the adverse effect of increasing corrosion rates with prolonged immersion. As a result, inhibition efficiency remains steady around 95% for all immersion times at 600 mg/L PNG. The proposed chemical interaction of some extract constituents with the mild steel surface at high PNG concentrations is supported by the pronounced anodic inhibiting effect of the extract (Figure 3a), which is often attributed to chemisorption of inhibitor species at anodic sites on the corroding metal surface.4,39,40 3.4. Theoretical Approach. Our experimental results show that the corrosion inhibiting action of PNG extract results from adsorption of the organic matter on the corroding mild steel surface. The often complex processes associated with metal inhibitor interactions can be theoretically investigated at the molecular level using computer simulations of suitable models in the framework of the density functional theory (DFT). We have performed such calculations to model the electronic and adsorption structures of some major phytochemical constituents of PNG extract as shown in Figure 7. These include pelargonidin (an anthocyanidin plant pigment), pelletierine (an alkaloid), and two phenolic acids (gallic acid and ellagic acid). The motivation for the computational studies is not so much to provide an indepth explanation of the adsorption of the extract, but rather to provide some insight into the nature of their individual interactions with the mild steel surface and their possible contributions to the overall inhibiting effect. 674
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HOMO locations, while the F+ sites correspond with the LUMO locations, indicating the zones through which the molecule would likely interact with the Fe surface. The adsorbability of a given molecule could be determined by its electronic structure or molecular size, respectively giving rise to chemical deactivation of active corrosion sites or geometric blocking. The former effect will be more pronounced if the functional groups in the molecule have a high tendency to donate electrons, as often reflected by the EHOMO and ELUMO values.4347 High values of EHOMO indicate the disposition of the molecule to donate electrons to an appropriate acceptor with vacant molecular orbitals. Similarly, low values of the gap ΔE = ELUMOHOMO, will render good inhibition efficiencies since the energy to remove an electron from the last occupied orbital will be minimized. The obtained values of EHOMO range from 6.81 to 3.76 eV, with pelargonidin having the highest value. The trend of ΔE is in the order perlagonidin < ellagic acid < pelletierine < gallic acid. The very low ΔE value obtained for pelargonidin (0.36 eV), coupled with the high EHOMO, suggests that the molecule would readily donate electrons to the metal surface and could thus play an important role in the chemisorption of the PNG extract on the metal surface. The trend of molecular size, which reflects the tendency of the molecules to function by a geometric blocking effect, decreased in the order ellagic acid > perlagonidin > pelletierine > gallic acid. This means that whereas pelargonidin should be the most strongly adsorbed from electronic structure considerations, ellargic acid is expected to be more strongly adsorbed from molecular size considerations. Forcite quench molecular dynamics was used to sample many different low energy adsorption configurations of the different molecules on Fe.48,49 The Fe crystal was cleaved along the (110) plane. Calculations were carried out in a 12 8 supercell using
We modeled the molecular electronic structures of the compounds, including the distribution of frontier molecular orbitals and Fukui indices, in order to establish the active sites as well as the local reactivity of the molecules. The calculations were performed by means of the DFT electronic structure program DMol3 using a Mulliken population analysis.41,42 Electronic parameters for the simulation include restricted spin polarization using the DND basis set and the PerdewWang (PW) local correlation density functional. Geometry optimization was achieved using the COMPASS force field and the Smart minimize method by high-convergence criteria. The electronic properties of ellargic acid, gallic acid, pelargonidin, and pelletierine, including the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and Fukui functions for electrophilic (F) and nucleophilic (F+) attack and total electron density are presented in Figure 8, while Table 3 provides some quantum chemical parameters related to the molecular electronic structures of the most stable conformations. The electron density is spread all around each molecule; hence we should expect flat-lying adsorption orientations. The local reactivity of the molecules as assessed from the Fukui indices (FI) show that the F sites for all the molecules correspond with the Table 4. Interaction Energies of Selected Phytochemical Constituents of PNG and Fe(110) Etotal molecule
(kcal/mol)
Emol
Ebind
(kcal/mol) EFe (kcal/mol) (kcal/mol)
pelargonidin
34.77
95.86
0.00
pelletierine gallic acid
142.20 99.06
58.15 18.09
0.00 0.00
ellagic acid
45.65
83.71
0.00
130.6 84.03 82.8 128.0
Figure 9. Representative snapshots from molecular dynamics models of (a) ellargic acid, (b) gallic acid, (c) pelargonidin, and (d) pelletierine; adsorption on Fe(110), emphasizing the soft epitaxial adsorption mechanism with accommodation of the molecular backbone in characteristic epitaxial grooves on the metal surface. 675
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the COMPASS force field and the Smart algorithm with NVE (microcanonical) ensemble, a time step of 1 fs, and simulation time 5 ps. Temperature was fixed at 350 K. Optimized structures of perlagonidin, ellagic acid, pelletierine, gallic acid, and Fe were used for the simulation. The system was quenched every 250 steps. Parts a, b, c, and d of Figure 9 show the optimized (lowest energy) adsorption structures for single molecules of ellargic acid, gallic acid, pelargonidin, and pelletierine, respectively, on the Fe(110) surface from our simulations. The molecules can be seen to maintain a flat-lying adsorption orientation on the Fe surface, as expected from the delocalization of the electron density all around the molecules. This orientation maximizes contact and hence augments the degree of surface coverage. To quantitatively appraise the interaction between each molecule and the Fe surface, the binding energy (Ebind) was calculated using the relationship in eq 11. A negative value of Ebind corresponds to a stable adsorption structure. Ebind ¼ Etotal ðEmol þ EFe Þ
ð11Þ
parameters associated with the electronic and adsorption structures of selected phytochemical components of the extract.
’ AUTHOR INFORMATION Corresponding Author
*Tel.: +234 (0) 803 7026581. E-mail:
[email protected] or
[email protected].
’ ACKNOWLEDGMENT This project is supported by TWAS, the Academy of Sciences for the Developing World, under the TWAS Grants for Research Units in Developing Countries Program (TWAS-RGA08-005) and the Education Trust Fund (ETF), and under batch one of ETF 2009/2010 research projects intervention for the Federal University of Technology Owerri. ’ REFERENCES (1) Ashassi-Sorkhabi, H.; Seifzadeh, D.; Hosseini, M. G. EN, EIS and polarization studies to evaluate the inhibition effect of 3H-phenothiazin3-one, 7-dimethylamin on mild steel corrosion in 1M HCl solution. Corros. Sci. 2008, 50, 3363. (2) Ameer, M. A.; Khamis, E.; Al-Senani, G. Adsorption studies of the effect of thiosemicarbazides on the corrosion of steel in phosphoric acid. Adsorpt. Sci. Technol. 2000, 18, 177. (3) Morad, M. S.; Kamal El-Dean, A. M. 2,20 -Dithiobis(3-cyano-4, 6-dimethylpyridine): A new class of acid corrosion inhibitors for mild steel. Corros. Sci. 2006, 48, 3398. (4) Popova, A.; Sokolova, E.; Raicheva, S.; Christov, M. AC and DC study of the temperature effect on mild steel corrosion in acid media in the presence of benzimidazole derivatives. Corros. Sci. 2003, 45, 33. (5) Moretti, G.; Guidi, F.; Grion, G. Tryptamine as a green iron corrosion inhibitor in 0.5 M deaerated sulphuric acid. Corros. Sci. 2004, 46, 387. (6) Tang, L.; Mu, G.; Liu, G. The effect of neutral red on the corrosion inhibition of cold rolled steel in 1.0 M hydrochloric acid. Corros. Sci. 2003, 45, 2251. (7) Shibli, S. M. A.; Saji, V. S. Co-inhibition characteristics of sodium tungstate with potassium iodate on mild steel corrosion. Corros. Sci. 2005, 47, 2213. (8) Kliskic, M.; Radosevic, J.; Gudic, S.; Katalinic, V. Aqueous extract of Rosmarinus officinalis L. as inhibitor of Al-Mg alloy corrosion in chloride solution. J. Appl. Electrochem. 2000, 30, 823. (9) Oguzie, E. E. Inhibition of acid corrosion of mild steel by Telfaria occidentalis extract. Pigm. Resin Technol. 2005, 34, 321. (10) Oguzie, E. E. Studies on the inhibitive effect of Occimum viridis extract on the acid corrosion of mild steel. Mater. Chem. Phys. 2006, 99, 441. (11) Oguzie, E. E. Adsorption and corrosion inhibitive properties of Azadirachta indica in acid solutions. Pigm. Resin Technol. 2006, 35, 334. (12) Oguzie, E. E. Corrosion inhibitive effect and adsorption behaviour of Hibiscus sabdariffa extract on mild steel in acidic media. Port. Electrochim. Acta 2008, 26, 303. (13) Gunasekaran, G.; Chauhan, L. R. Eco friendly inhibitor for corrosion inhibition of mild steel in phosphoric acid medium. Electrochim. Acta 2004, 49, 4387. (14) Okafor, P. C.; Ikpi, M. E.; Uwah, I. E.; Ebenso, E. E.; Ekpe, U. J.; Umoren, S. A. Inhibitory action of Phyllantus amarus extracts on the corrosion of mild steel in acidic media. Corros. Sci. 2008, 50, 2310. (15) Abiola, O. K.; James, A. O. The effects of Aloe vera extract on corrosion and kinetics of corrosion process of zinc in HCl solution. Corros. Sci. 2010, 52, 661. (16) Satapathy, A. K.; Gunasekaran, G.; Sahoo, S. C.; Amit, K.; Rodrigues, P. V. Corrosion inhibition by Justicia gendarussa plant extract in hydrochloric acid solution. Corros. Sci. 2009, 51, 2848.
Emol, EFe, and Etotal correspond respectively to the total energies of the molecule, Fe(110) slab, and the adsorbed molecule/ Fe(110) couple. The obtained values are given in Table 4. In each case the potential energies were calculated by averaging the energies of the five structures of lowest energy. Since the surface atoms in the Fe(110) slab are constrained, the energy of the forces between them remains steady throughout the simulation and is excluded from the calculation since they will not affect the overall motion of the adsorbed molecule. Hence, the energy of the constrained Fe(110) surface is given as zero. The trend of Ebind (perlagonidin < ellagic acid < pelletierine < gallic acid) confirms a predominant influence of electronic interactions in the adsorption of pelargonidin. Besides this, the trend of Ebind, ΔE, and molecular size for the other three molecules coincide. Close inspection of the adsorption structures in Figure 9 reveals adsorption configurations in which polarizable atoms (C, N, O, S) along the backbone of the adsorbate molecules are preferentially accommodated in characteristic epitaxial grooves on the metal surface, avoiding contact with the Fe atoms on the surface plane (larger spheres on the Fe(110) slab). Such epitaxial adsorption orientation is associated with a minimum free energy of adsorption, and adsorption strength improves with improved fit of the polarizable atoms of a molecule to multiple epitaxial sites.50 This phenomenon accounts for the obtained high binding energies of the phytochemical constituents of PNG, hence the remarkable corrosion inhibiting effect of the extract.
4. CONCLUSIONS P. granatum (PNG) extract effectively inhibited mild steel corrosion in 1 M HCl and 0.5 M H2SO4 solutions. Impedance results revealed that the extract functioned via adsorption of the organic matter on the metal/solution interface. Extract adsorption was further corroborated by the experimental data fit to the Langmuir isotherm. Polarization measurements show that the adsorbed extract organic matter inhibited the corrosion process via a mixed-inhibition mechanism, affecting both the anodic metal dissolution reaction and the cathodic hydrogen evolution reaction. Inhibition efficiency improved with the extract concentration but decreased with prolonged exposure. Inhibition efficiency at high extract concentration was independent of exposure time in 0.5 M H2SO4. The inhibiting potential of PNG extract was theoretically confirmed via DFT based quantum chemical computations of 676
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Synergistic effect of methionine and iodide ion. Electrochim. Acta 2007, 52, 6988. (39) Oguzie, E. E.; Onuoha, G. N.; Onuchukwu, A. I. Inhibitory mechanism of mild steel corrosion in 2M sulphuric acid solution by methylene blue dye. Mater. Chem. Phys. 2004, 89, 305. (40) Harek, Y.; Larabi, L. Corrosion inhibition of mild steel in 1 mol dm-3 HCl by oxalic N-phenylhydrazide N0 -phenylthiosemicarbazide. Kem. Ind. 2004, 53, 55. (41) Delley, B. J. An all-electron numerical method for solving the local density functional for polyatomic molecules. Chem. Phys. 1990, 92, 508. (42) Delley, B. J. From molecules to solids with the Dmol3 approach. Chem. Phys. 2000, 113, 7756. (43) Martinez, S.; Stagljar, I. S. Correlation between the molecular structure and the corrosion inhibition efficiency of chestnut tannin in acidic solutions. THEOCHEM 2003, 640, 167. (44) Khaled, K. F.; Babic-Samardzija, K.; Hackerman, N. Theoretical study of the structural effects of polymethylene amines on corrosion inhibition of iron in acid solutions. Electrochim. Acta 2005, 50, 2515. (45) Rodrıguez-Valdez, L. M.; Villamisar, W.; Casales, M.; Gonzalez-Rodriguez, J. G.; Martınez-Villafane, A.; Martinez, L.; Glossman-Mitnik, D. Computational simulations of the molecular structure and corrosion properties of amidoethyl, aminoethyl and hydroxyethyl imidazolines inhibitors. Corros. Sci. 2006, 48, 4053. (46) Cruz, J.; Pandiyan, T.; Garcia-Ochoa, E. A new inhibitor for mild carbon steel: electrochemical and DFT studies. J. Electroanal. Chem. 2005, 583, 8. (47) Fu, J.; Li, S.; Wang, Y.; Cao, L.; Lu, L. Computational and electrochemical studies of some amino acid compounds as corrosion inhibitors for mild steel in hydrochloric acid solution. J. Mater. Sci. 2010, 45, 6255. (48) Casewit, C. J.; Colwell, K. S.; Rappe, A. K. Application of universal force field to organic molecules. J. Am. Chem. Soc. 1992, 114, 10035. (49) Casewit, C. J.; Colwell, K. S.; Rappe, A. K. Application of universal force field to main group elements. J. Am. Chem. Soc. 1992, 114, 10046. (50) Heinz, H.; Farmer, B. L.; Pandey, R. B.; Slocik, J. M.; Patnaik, S. S.; Pachter, R.; Naik, R. R. Nature of molecular interactions of peptides with gold, palladium, and Pd-Au bimetal surfaces in aqueous solution. J. Am. Chem. Soc. 2009, 131, 9704.
(17) Quraishi, M.A.; Singh, A.; Singh, V. K.; Yadav, D. K.; Singh, A. K. Green approach to corrosion inhibition of mild steel in hydrochloric acid and sulphuric acid solutions by the extract of Murraya koenigii leaves. Mater. Chem. Phys. 2010, 122, 114. (18) Bothi Raja, P.; Sethuraman, M. G. Inhibitive effect of black pepper extract on the sulphuric acid corrosion of mild steel. Mater. Lett. 2008, 62, 2977. (19) Kalaiselvi, P.; Chellammal, S.; Palanichamy, S.; Subramanian, G. Artemisia pallens as corrosion inhibitor for mild steel in HCl medium. Mater. Chem. Phys. 2010, 120, 643. (20) Ekanem, U. F.; Umoren, S. A.; Udousoro, I. I.; Udoh, A. P. Inhibition of mild steel corrosion in HCl using pineapple leaves (Ananas comosus L.) extracts. J. Mater. Sci. 2010, 45, 5558. (21) Umoren, S. A.; Obot, I. B.; Obi-Egbedi, N. O. Raphia hookeri gum as a potential eco-friendly inhibitor for mild steel in sulfuric acid. J. Mater. Sci. 2009, 44, 274. (22) Ostovari, A.; Hoseinieh, S. M.; Peikari, M.; Shadizadeh, S. R.; Hashemi, S. J. Corrosion inhibition of mild steel in 1M HCl solution by henna extract: A comparative study of the inhibition by henna and its constituents (Lawsone, Gallicacid, a-D-Glucose and Tannicacid). Corros. Sci. 2009, 51, 1935. (23) Cardozo da Rocha, J.; da Cunha Ponciano Gome, J.; D’Elia, E. Corrosion inhibition of carbon steel in hydrochloric acid solution by fruit peel aqueous extracts. Corros. Sci. 2010, 52, 2341. (24) Rosliza, R.; Wan Nik, W. B. Improvement of corrosion resistance of AA6061 alloy by tapioca starch in sea water. Curr. Appl. Phys. 2010, 10, 221. (25) Gece, G. The use of quantum chemical methods in corrosion inhibitor studies. Corros. Sci. 2008, 52, 2981. (26) Oguzie, E. E.; Wang, S. G.; Li, Y.; Wang, F. H. Influence of iron microstructure on corrosion inhibitor performance in acidic media. J. Phys. Chem. C 2009, 113, 8420. (27) Obot, I. B.; Obi-Egbedi, N. O. Adsorption properties and inhibition of mild steel corrosion in sulphuric acid solution by ketoconazole: Experimental and theoretical investigation. Corros. Sci. 2010, 52, 198. (28) Kokalj, A.; Peljhan, S. Density Functional Theory Study of ATA, BTAH, and BTAOH as Copper Corrosion Inhibitors: Adsorption onto Cu(111) from Gas Phase. Langmuir 2010, 26, 14582. (29) Khaled, K. F. Studies of iron corrosion inhibition using chemical, electrochemical and computer simulation techniques. Electrochim. Acta 2010, 55, 6523. (30) Oguzie, E. E.; Enenebeaku, C. K.; Akalezi, C. O.; Okoro, S. C.; Ayuk, A. A.; Ejike, E. N. Adsorption and Corrosion inhibiting effect of Dacryodis edulis extract on low carbon steel corrosion in acidic media. J. Colloid Interface Sci. 2010, 349, 283. (31) Oguzie, E. E.; Li, Y.; Wang, F. H. Corrosion inhibition and adsorption behaviour of methionine on mild steel in sulphuric acid and synergistic effect of iodide ion. J. Colloid Interface Sci. 2007, 310, 90. (32) Kissi, M.; Bouklah, M.; Hammouti, B.; Benkaddour, M. Synergistic effect of iodide ions on the corrosion inhibition of steel in 0.5 M H2SO4 by new chalcone derivatives. Appl. Surf. Sci. 2006, 252, 4190. (33) Wang, R.; Wang, W.; Wang, L.; Liu, R.; Ding, Y.; Du, L. Constituents of the flowers of Punica granatum. Fitoterapia 2006, 77, 534. (34) Nawwar, M. A. M.; Hussein, S. A. M.; Merfort, I. NMR spectral analysis of polyphenols from Punica granatum. Phytochemistry 1994, 36, 793. (35) El-Toumy, S. A. A.; Rauwald, H. W. Two ellagitannins from Punica granatum heartwood. Phytochemistry 2002, 61, 971. (36) Rena, K.; Palida, A.; Zhang, X. Y. Studies on the chemical constituents from Xinjiang Punica granatum. J. Chin. Med. Mater. 2009, 32, 363. (37) Villamil, R. F. V.; Corio, P.; Agostinho, S. M. L.; Rubim, J. C. Effect of sodium dodecylsulphate on copper corrosion in sulphuric acid media in the absence and presence of benzotriazole. J. Electroanal. Chem. 1999, 472, 112. (38) Oguzie, E. E.; Li, Y.; Wang, F. H. Effect of surface nanocrystallization on corrosion and corrosion inhibition of low carbon steel: 677
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