- Email: [email protected]
Passive Thin Film Coating through Electrodeposition of Salicylideneaniline
Available online at www.sciencedirect.com
APCBEE Procedia 3 (2012) 104 – 109
ICCCP 2012: 5-6 May M 2012, Kuala Lum mpur, Malaysia
Passivve Thin Film F Coating thrrough Ellectrodeppositionn of Salicylidenneanilinee a,, Zailelah Zainoldin Z *, Moham mad Kamal Haruna, Haadariah Baahrona, Karrimah ma Kassim a
F Faculty of Appliedd Sciences, Univeersiti Teknologi MARA, M 40450 Sha ah Alam, Selangoor, Malaysia
Absttract Basicc salicylideneaaniline compouund was electrro-oxidized using mild steel electrode throough cyclic vooltammetry in alkalline medium. Scanning S Electrron Microscopyy analysis indiccates the formattion of thin orgganic film that high in ionic impeedance. Currennt suppression detected d in the cyclic c voltamm mogram during the t five CV cyccles indicates aan irreversible reacttion with the miild steel surfacee becoming moore passive withh increase in number of cycles increased. Thiss is due to the form mation of organic layer on the mild m steel surfaace that acts as a barrier for thee electron transffer and makingg it difficult to furthher oxidize saliccylideneaniline.. Surface morphhology of salicyylideneaniline deposited d on mild m steel surface was studied by sccanning electronn microscopy (SEM). The effeect of scan rate potential on the deposition off salicylideneaniline was also studiied. The currentt peak increases with increase in scan rate annd the peak also o shifted to the more positive ppotentials due to thee diffusion-conntrolled process.. Slow scan ratee was favored for f optimum eleectrodeposition of salicylideneaniline.
© 2012 20012 Published Publisheddby byElsevier ElsevierB.V. B Selection B.V. Selection n and/or peer r under review under responsibility of Asia-Pacif fic © and/or peer review responsibility of yAsia-Pacifi c Chemical, Chem mical, & Biolog ical & Enviro onmental Society Engiineering Socieety Biological Environmental Engineering Keyw words: Electrodepposition, Salicyliddeneaniline, Mild Steel, Cyclic Vooltammetry, Sem
1. In ntroduction E Electrodepositi ion method haas been widelly used in manny research field including biosensor [155], corrosion proteection [5,7,9,,12], electro-ccatalysis [2], electrochrom mic [14] and batteries [10]. Electrodepposition is a
* Corresponding author. a Tel.: +6033-55443300; fax: +603-5544-32100. E E-mail address: [email protected]
2212-6708© 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of Asia-Pacific Chemical, Biological & Environmental Engineering Society doi:10.1016/j.apcbee.2012.06.054
Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
105
method used to deposit organic film from electroactives monomers on a substrate. The method is controllable and yet promises a good quality film formation [6]. Generally, three different techniques were employed and they are cyclic voltammetry, chronoamperometry, and chronopotentiometry. A successful electrode fouling can be determined by various experimental parameters including the monomer concentrations, pH, the scan rate, the upper potential limit, the electrochemical techniques, and the solvent [4,12]. In this work, cyclic voltammetry (CV) was carried out in order to electrodeposit salicylideneaniline onto the mild steel substrate. Salicylideneaniline is part of the azomethine group containing C double bond N (C=N) connected to the aryl or alkyl group. Hydroxyl group (-OH) on the ring makes the deposition of salicylideneaniline become possible. The purpose of the study is to modify the mild steel surface by depositing non-conductive organic film on the mild steel surface by simple electrochemical method. 2. Experimental Salicylideneaniline was synthesized by reacting salicylaldehyde with aniline at 1:1 ratio in the absence of solvent, producing yellow solid compound according to method developed by Saggiomo and coworkers [11]. Fig. 1. shows the chemical structure of salicylideneaniline.
HO
N
Fig. 1. Chemical structure of salicylideneaniline
A three-electrode system was used throughout this study. A silver/silver chloride (Ag/AgCl) reference electrode, platinum electrode counter electrode, and mild steel working electrode with a composition (in wt%) C 0.05; Fe 99.63; Mn 0.23; P 0.02; S 0.02; Si 0.05. The surface area of mild steel electrode was 1cm2. The mild steel working electrodes were polished up to 1200 after which it was then diamond polished to 1μm before each experiment. They were washed with distilled water, degreased with acetone and ethanol, and finally dried and stored in desiccator before used. The electrodeposition was carried out using cyclic voltammetry (CV) technique in 0.3 M sodium hydroxide solution (70% distilled water: 30% ethanol) containing 0.1 M salicylideneaniline. The pH of the solution is adjusted to pH 12. The alkaline medium was chosen for electrodeposition process as mild steel remains passive in basic medium. The electrolytes were freshly prepared before each experiment. All chemicals used were analytical grade obtained from Sigma Aldrich. All cyclic voltammetry were carried out using Metrohm Autolab potentiostat-galvanostat PGSTAT 302N connected to the Nova 1.7 software. 3. Results and discussion 3.1. Cyclic voltammetry on mild steel electrode Fig. 2.(a) shows the cyclic voltammogram of mild steel electrode immersed in 0.3M sodium hydroxide (70%
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Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
distilled water: 30% ethanol) solution. It was carried out at a potential range of -0.5 V (versus Ag/AgCl) to +1.6 V (versus Ag/AgCl) and reversed back to -0.5V (versus Ag/AgCl) at a scan rate of 50mVs-1. Based on the cyclic voltammogram, there was no oxidation reaction until it reach the potential of +0.6V (versus Ag/AgCl). The current start to rise above the potential of +0.6V (versus Ag/AgCl) due to oxidation of the mild steel [3]. Fig. 2.(b) shows the cyclic voltammogram of mild steel electrode immersed in 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution containing 0.1M salicylideneaniline. Five CV cycles were carried out in order to electrodeposit salicylideneaniline onto the mild steel at the potential range of -0.5V (versus Ag/AgCl) to +2.0V (versus Ag/AgCl) at a scan rate of 50mVs-1. A brownish color was observed on the mild steel surface as the current start to increase during the first CV cycle. The color darkened as the number of cycles increased. This could be due to the increasing amount of material formed on the mild steel surface. (a)
65
(b)
45
Current, i (mA cm2)
Current, i (mA cm-2)
55
35 25 15 5
35 30 25 20 15 10 5 -1
-5 -0.6
-0.3
0
0.3
0.6
0.9
Potential, E (V vs Ag/AgCl)
1.2
1.5
1.8
-0.6
-0.1
0.4
0.9
1.4
1.9
2.4
Potential, E (V vs. Ag/AgCl)
Fig. 2. Cyclic voltammograms of mild steel electrode in (a) 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution (b) 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution containing 0.1M salicylideneaniline. Scan rate of 50mVs-1.
As shown in the figure, all the five CV cycles shows irreversible wave indicating no reduction reaction occurs during the test. During the first cycle, the current start to rise quickly as the potential reach +0.6V (versus Ag/AgCl) and further increase until it reach the maximum current of 0.032A and suddenly the current drop rapidly as the potential go above the +1.79V (versus Ag/AgCl). Current suppression can be seen as the number of cycle increased. This is due to the passivation of the mild steel surface which leads to the suppression of current. The mild steel surface becomes passive caused by the deposition of and insulative layer of salicylideneaniline on the mild steel surface during the electrodeposition process. Electrodeposition process become difficult as the active surface on the anode electrode decreased [1,8,13] making it difficult for electron transfer to occur indicated by the suppression of current on the cyclic voltammogram. The surface morphology of salicylideneaniline deposited on the mild steel surface was observed by scanning electron microscope (SEM). After the electrodeposition process, the sample was cleaned using distilled water, dried and stored in desiccator. An SEM analysis was carried out with the result shown in Fig. 3. The results show good coverage of the mild steel surface by the organic film. This is consistent with the cyclic voltammetry behavior which shows the current suppression after the first potential cycle indicating the formation of organic film on the mild steel surface that act as a barrier for the oxidation to occur.
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Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
(a)
(b)
Fig. 3. Scanning electron micrographs after the electrodeposition of salicylideneaniline on the mild steel surface. (a) Top view with enlargement factor of 100000 times, (b) Cross-section with enlargement factor of 5000 times.
3.2. The effect of scan rate Fig. 4. shows the first cyclic voltammograms during the electrodeposition of 0.1M salicylideneaniline on the mild steel surface in 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution studied at different scan rate. The voltammograms indicates that as the scan rate potential increased the current peak increases and also shifted to more positive potentials. The observations agree with the previous electropolymerization studies on the effect of scan rate [1,12]. Brownish color was observed on the mild steel surface although different scan rate potentials were used. 35
50 mVs-1
Current, i (mA cm-2)
30
25 mVs-1
25
10 mVs-1
20 15
5 mVs-1
10 5 0 -5 -0.6 -0.3
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
Potential, E (V vs. Ag/AgCl)
Fig. 4. First Cyclic voltammograms of mild steel in 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution containing 0.1M salicylideneaniline at various scan rate.
Fig. 5.(a) shows that the increase in peak current is proportional to the square root of scan rate, Ȟ1/2 . This indicates a diffusion-controlled process. There are two possibilities how salicylideneaniline molecules react, first is through the diffusion of free molecules to the electrode surface and second is through the adsorption of the molecules on the mild steel surface [12]. Fig. 5(b) shows a parallel relation between the peak potential, Ep and logarithms of scan rate, log Ȟ where it indicates the irreversible reaction during oxidation of salicylideneaniline [12]. The linear regression equation is Ep (V) = 0.634 + 0.659 log Ȟ (mVs-1)
(1)
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Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109 40
(b)
35 R² = 0.906
30
Peak potential, Ep (V)
Current, i (mA cm2)
(a)
25 20 15 10 5
2 R² = 0.979
1.5 1 0.5 0
0 0
0.05
0.1
0.15
0.2
Ȟ1/2 (V s-1)1/2
0.25
0
0.5
1
1.5
2
log Ȟ (mV s-1)
Fig. 5. (a) Graph of current densities, i versus square root of the scan rate, Ȟ1/2 and (b) graph of peak potential, Ep versus logarithm of the scan rate, log Ȟ.
4. Conclusion Electrodeposition of salicylideneaniline shows irreversible peak of cyclic voltammogram indicates that only oxidation reaction occurs. Strong current reduction was observed after the first potential cycle showing that the active site on the mild steel surface has been passivated by the organic film. SEM results indicate that organic film was formed on the mild steel surface. Brownish color was observed on the mild steel surface during the oxidation of salicylideneaniline even though different scan rate potentials were used. This shows that oxidation reaction still occurring even at different scan rate. The current peak shifted to more positive potentials at higher scan rate potential due to the diffusion controlled process. Corrosion study will be conducted after the surface modification to measure it effectiveness against corrosion. Surface modification via formation of organic passive layers is an alternative approach in developing an optimum corrosion protective layer particularly in acidic or marine conditions. Acknowledgements Authors are highly thankful to the Ministry of Higher Education of Malaysia for the research grant 600RMI/ST/FRGS/5/3/Fst (11/2009), Universiti Teknologi MARA for the scholarship, and the Faculty of Applied Sciences, UiTM Shah Alam for the research facilities. References [1] Bao L., Xiong R., Wei G. Electrochemical polymerization of phenol on 304 stainless steel anodes and subsequent coating structure analysis. Electrochim. Acta 2010; 55: 4030-4038. [2] Deletioglu D., Yalcinkaya S., Demetgul C., Timur M., Serin S. Electropolymerization of Cu11-(N,N’-bis(3-methoxysalicylidene)2-aminobenzylamine) on platinum electrode: application to the electrocatalytic reduction of hydrogen peroxide. Mat. Chem. and Phy. 2011; 128: 500-506. [3] Harun M.K., Lyon S.B., Marsh J. Formation and characterisation of thin phenolic amine-functional electropolymers on a mild steel substrate. Prog. in Org. Coat. 2005; 52: 246-252. [4] Hur E., Bereket G., Duran B., Ozdemir D., Sahin Y. Electropolymerization of m-aminophenol on mild steel and its corrosion protection effect. Prog. in Org. Coat. 2007; 60: 153-160. [5] Flamini D.O., Saidman S.B. Electrodeposition of polypyrrole onto NiTi and the corrosion behavior of the coated alloy. Corros. Sci. 2010; 52: 229-234.
Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
[6] Inzelt G., Pineri M., Schultze J.W., Vorotyntsev M.A. Electron and proton conducting polymers: recent developments and prospects. Electrochim. Acta 2000; 45: 2403-2421. [7] Kowalski D., Ueda M., Ohtsuka T. The effect of ultrasonic irradiation during electroplymerization of polypyrrole on corrosion prevention of the coated steel. Corros. Sci. 2008; 50: 286-291. [8] Muthirulan P., Rajendran N. Poly(ο-phenylenediamine) coatings on mild steel: electrosynthesis, characterization and its corrosion protection ability in acid medium. Surf. Coat. Technol. 2012; 206: 2072-2078. [9] Narayanasamy B., Rajendran S. Electropolymerized bilayer coatings of polyaniline and poly(N-methylaniline) on mild steel and their corrosion protection performance. Prog. in Org. Coat. 2010; 67: 246-254. [10] Osaka T., Momma T. Impedance analysis of electropolymerized conducting polymers for polymer battery cathodes. Electrochim. Acta 1993; 38: 2011-2014. [11] Saggiomo V., Luning U. On the formation of imines in water- a comparison. Tet. Letters 2009; 50:4663-4665. [12] Samet Y., Kraiem D., Abdelhedi R. Electropolymerization of phenol, ο-nitrophenol and ο-methoxyphenol on gold and carbon steel materials and their corrosion protection effects. Prog. in Org. Coat. 2010; 69: 335-343. [13] Tahar N.B., Savall A. Electropolymerization of phenol on a vitreous carbon electrode in alkaline aqueous solution at different temperatures. Electrochim. Acta 2009; 55: 465-469. [14] Wang B., Kong T., Zhao J., Cui C., Liu R., He Q. Synthesis and electropolymerization of 1,4-bis(2-thienyl)-2,5-difluorobenzene and its electrochromic properties and electrochromic device application. Int. J. Electrochem. Sci. 2012; 7: 615-630. [15] Yang R., Ruan C., Dai W., Deng J., Kong J. Electropolymerization of thionine in neutral aqueous media and H2O2 biosensor based on poly(thionine). Electrochim. Acta 1999; 44: 1585-1596.
109
APCBEE Procedia 3 (2012) 104 – 109
ICCCP 2012: 5-6 May M 2012, Kuala Lum mpur, Malaysia
Passivve Thin Film F Coating thrrough Ellectrodeppositionn of Salicylidenneanilinee a,, Zailelah Zainoldin Z *, Moham mad Kamal Haruna, Haadariah Baahrona, Karrimah ma Kassim a
F Faculty of Appliedd Sciences, Univeersiti Teknologi MARA, M 40450 Sha ah Alam, Selangoor, Malaysia
Absttract Basicc salicylideneaaniline compouund was electrro-oxidized using mild steel electrode throough cyclic vooltammetry in alkalline medium. Scanning S Electrron Microscopyy analysis indiccates the formattion of thin orgganic film that high in ionic impeedance. Currennt suppression detected d in the cyclic c voltamm mogram during the t five CV cyccles indicates aan irreversible reacttion with the miild steel surfacee becoming moore passive withh increase in number of cycles increased. Thiss is due to the form mation of organic layer on the mild m steel surfaace that acts as a barrier for thee electron transffer and makingg it difficult to furthher oxidize saliccylideneaniline.. Surface morphhology of salicyylideneaniline deposited d on mild m steel surface was studied by sccanning electronn microscopy (SEM). The effeect of scan rate potential on the deposition off salicylideneaniline was also studiied. The currentt peak increases with increase in scan rate annd the peak also o shifted to the more positive ppotentials due to thee diffusion-conntrolled process.. Slow scan ratee was favored for f optimum eleectrodeposition of salicylideneaniline.
© 2012 20012 Published Publisheddby byElsevier ElsevierB.V. B Selection B.V. Selection n and/or peer r under review under responsibility of Asia-Pacif fic © and/or peer review responsibility of yAsia-Pacifi c Chemical, Chem mical, & Biolog ical & Enviro onmental Society Engiineering Socieety Biological Environmental Engineering Keyw words: Electrodepposition, Salicyliddeneaniline, Mild Steel, Cyclic Vooltammetry, Sem
1. In ntroduction E Electrodepositi ion method haas been widelly used in manny research field including biosensor [155], corrosion proteection [5,7,9,,12], electro-ccatalysis [2], electrochrom mic [14] and batteries [10]. Electrodepposition is a
* Corresponding author. a Tel.: +6033-55443300; fax: +603-5544-32100. E E-mail address: [email protected]
2212-6708© 2012 Published by Elsevier B.V. Selection and/or peer review under responsibility of Asia-Pacific Chemical, Biological & Environmental Engineering Society doi:10.1016/j.apcbee.2012.06.054
Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
105
method used to deposit organic film from electroactives monomers on a substrate. The method is controllable and yet promises a good quality film formation [6]. Generally, three different techniques were employed and they are cyclic voltammetry, chronoamperometry, and chronopotentiometry. A successful electrode fouling can be determined by various experimental parameters including the monomer concentrations, pH, the scan rate, the upper potential limit, the electrochemical techniques, and the solvent [4,12]. In this work, cyclic voltammetry (CV) was carried out in order to electrodeposit salicylideneaniline onto the mild steel substrate. Salicylideneaniline is part of the azomethine group containing C double bond N (C=N) connected to the aryl or alkyl group. Hydroxyl group (-OH) on the ring makes the deposition of salicylideneaniline become possible. The purpose of the study is to modify the mild steel surface by depositing non-conductive organic film on the mild steel surface by simple electrochemical method. 2. Experimental Salicylideneaniline was synthesized by reacting salicylaldehyde with aniline at 1:1 ratio in the absence of solvent, producing yellow solid compound according to method developed by Saggiomo and coworkers [11]. Fig. 1. shows the chemical structure of salicylideneaniline.
HO
N
Fig. 1. Chemical structure of salicylideneaniline
A three-electrode system was used throughout this study. A silver/silver chloride (Ag/AgCl) reference electrode, platinum electrode counter electrode, and mild steel working electrode with a composition (in wt%) C 0.05; Fe 99.63; Mn 0.23; P 0.02; S 0.02; Si 0.05. The surface area of mild steel electrode was 1cm2. The mild steel working electrodes were polished up to 1200 after which it was then diamond polished to 1μm before each experiment. They were washed with distilled water, degreased with acetone and ethanol, and finally dried and stored in desiccator before used. The electrodeposition was carried out using cyclic voltammetry (CV) technique in 0.3 M sodium hydroxide solution (70% distilled water: 30% ethanol) containing 0.1 M salicylideneaniline. The pH of the solution is adjusted to pH 12. The alkaline medium was chosen for electrodeposition process as mild steel remains passive in basic medium. The electrolytes were freshly prepared before each experiment. All chemicals used were analytical grade obtained from Sigma Aldrich. All cyclic voltammetry were carried out using Metrohm Autolab potentiostat-galvanostat PGSTAT 302N connected to the Nova 1.7 software. 3. Results and discussion 3.1. Cyclic voltammetry on mild steel electrode Fig. 2.(a) shows the cyclic voltammogram of mild steel electrode immersed in 0.3M sodium hydroxide (70%
106
Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
distilled water: 30% ethanol) solution. It was carried out at a potential range of -0.5 V (versus Ag/AgCl) to +1.6 V (versus Ag/AgCl) and reversed back to -0.5V (versus Ag/AgCl) at a scan rate of 50mVs-1. Based on the cyclic voltammogram, there was no oxidation reaction until it reach the potential of +0.6V (versus Ag/AgCl). The current start to rise above the potential of +0.6V (versus Ag/AgCl) due to oxidation of the mild steel [3]. Fig. 2.(b) shows the cyclic voltammogram of mild steel electrode immersed in 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution containing 0.1M salicylideneaniline. Five CV cycles were carried out in order to electrodeposit salicylideneaniline onto the mild steel at the potential range of -0.5V (versus Ag/AgCl) to +2.0V (versus Ag/AgCl) at a scan rate of 50mVs-1. A brownish color was observed on the mild steel surface as the current start to increase during the first CV cycle. The color darkened as the number of cycles increased. This could be due to the increasing amount of material formed on the mild steel surface. (a)
65
(b)
45
Current, i (mA cm2)
Current, i (mA cm-2)
55
35 25 15 5
35 30 25 20 15 10 5 -1
-5 -0.6
-0.3
0
0.3
0.6
0.9
Potential, E (V vs Ag/AgCl)
1.2
1.5
1.8
-0.6
-0.1
0.4
0.9
1.4
1.9
2.4
Potential, E (V vs. Ag/AgCl)
Fig. 2. Cyclic voltammograms of mild steel electrode in (a) 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution (b) 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution containing 0.1M salicylideneaniline. Scan rate of 50mVs-1.
As shown in the figure, all the five CV cycles shows irreversible wave indicating no reduction reaction occurs during the test. During the first cycle, the current start to rise quickly as the potential reach +0.6V (versus Ag/AgCl) and further increase until it reach the maximum current of 0.032A and suddenly the current drop rapidly as the potential go above the +1.79V (versus Ag/AgCl). Current suppression can be seen as the number of cycle increased. This is due to the passivation of the mild steel surface which leads to the suppression of current. The mild steel surface becomes passive caused by the deposition of and insulative layer of salicylideneaniline on the mild steel surface during the electrodeposition process. Electrodeposition process become difficult as the active surface on the anode electrode decreased [1,8,13] making it difficult for electron transfer to occur indicated by the suppression of current on the cyclic voltammogram. The surface morphology of salicylideneaniline deposited on the mild steel surface was observed by scanning electron microscope (SEM). After the electrodeposition process, the sample was cleaned using distilled water, dried and stored in desiccator. An SEM analysis was carried out with the result shown in Fig. 3. The results show good coverage of the mild steel surface by the organic film. This is consistent with the cyclic voltammetry behavior which shows the current suppression after the first potential cycle indicating the formation of organic film on the mild steel surface that act as a barrier for the oxidation to occur.
107
Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109
(a)
(b)
Fig. 3. Scanning electron micrographs after the electrodeposition of salicylideneaniline on the mild steel surface. (a) Top view with enlargement factor of 100000 times, (b) Cross-section with enlargement factor of 5000 times.
3.2. The effect of scan rate Fig. 4. shows the first cyclic voltammograms during the electrodeposition of 0.1M salicylideneaniline on the mild steel surface in 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution studied at different scan rate. The voltammograms indicates that as the scan rate potential increased the current peak increases and also shifted to more positive potentials. The observations agree with the previous electropolymerization studies on the effect of scan rate [1,12]. Brownish color was observed on the mild steel surface although different scan rate potentials were used. 35
50 mVs-1
Current, i (mA cm-2)
30
25 mVs-1
25
10 mVs-1
20 15
5 mVs-1
10 5 0 -5 -0.6 -0.3
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
Potential, E (V vs. Ag/AgCl)
Fig. 4. First Cyclic voltammograms of mild steel in 0.3M sodium hydroxide (70% distilled water: 30% ethanol) solution containing 0.1M salicylideneaniline at various scan rate.
Fig. 5.(a) shows that the increase in peak current is proportional to the square root of scan rate, Ȟ1/2 . This indicates a diffusion-controlled process. There are two possibilities how salicylideneaniline molecules react, first is through the diffusion of free molecules to the electrode surface and second is through the adsorption of the molecules on the mild steel surface [12]. Fig. 5(b) shows a parallel relation between the peak potential, Ep and logarithms of scan rate, log Ȟ where it indicates the irreversible reaction during oxidation of salicylideneaniline [12]. The linear regression equation is Ep (V) = 0.634 + 0.659 log Ȟ (mVs-1)
(1)
108
Zailelah Zainoldin et al. / APCBEE Procedia 3 (2012) 104 – 109 40
(b)
35 R² = 0.906
30
Peak potential, Ep (V)
Current, i (mA cm2)
(a)
25 20 15 10 5
2 R² = 0.979
1.5 1 0.5 0
0 0
0.05
0.1
0.15
0.2
Ȟ1/2 (V s-1)1/2
0.25
0
0.5
1
1.5
2
log Ȟ (mV s-1)
Fig. 5. (a) Graph of current densities, i versus square root of the scan rate, Ȟ1/2 and (b) graph of peak potential, Ep versus logarithm of the scan rate, log Ȟ.
4. Conclusion Electrodeposition of salicylideneaniline shows irreversible peak of cyclic voltammogram indicates that only oxidation reaction occurs. Strong current reduction was observed after the first potential cycle showing that the active site on the mild steel surface has been passivated by the organic film. SEM results indicate that organic film was formed on the mild steel surface. Brownish color was observed on the mild steel surface during the oxidation of salicylideneaniline even though different scan rate potentials were used. This shows that oxidation reaction still occurring even at different scan rate. The current peak shifted to more positive potentials at higher scan rate potential due to the diffusion controlled process. Corrosion study will be conducted after the surface modification to measure it effectiveness against corrosion. Surface modification via formation of organic passive layers is an alternative approach in developing an optimum corrosion protective layer particularly in acidic or marine conditions. Acknowledgements Authors are highly thankful to the Ministry of Higher Education of Malaysia for the research grant 600RMI/ST/FRGS/5/3/Fst (11/2009), Universiti Teknologi MARA for the scholarship, and the Faculty of Applied Sciences, UiTM Shah Alam for the research facilities. References [1] Bao L., Xiong R., Wei G. Electrochemical polymerization of phenol on 304 stainless steel anodes and subsequent coating structure analysis. Electrochim. Acta 2010; 55: 4030-4038. [2] Deletioglu D., Yalcinkaya S., Demetgul C., Timur M., Serin S. Electropolymerization of Cu11-(N,N’-bis(3-methoxysalicylidene)2-aminobenzylamine) on platinum electrode: application to the electrocatalytic reduction of hydrogen peroxide. Mat. Chem. and Phy. 2011; 128: 500-506. [3] Harun M.K., Lyon S.B., Marsh J. Formation and characterisation of thin phenolic amine-functional electropolymers on a mild steel substrate. Prog. in Org. Coat. 2005; 52: 246-252. [4] Hur E., Bereket G., Duran B., Ozdemir D., Sahin Y. Electropolymerization of m-aminophenol on mild steel and its corrosion protection effect. Prog. in Org. Coat. 2007; 60: 153-160. [5] Flamini D.O., Saidman S.B. Electrodeposition of polypyrrole onto NiTi and the corrosion behavior of the coated alloy. Corros. Sci. 2010; 52: 229-234.
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