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Electroactive poly(aromatic amine) films deposited on mild steel
SyntheticMetals102(1999)13961391
Electroactive poly(aromatic amine) films deposited on mild steel A. Meneguzzi”, M. C. Pham”,‘, C. A. Ferreiraa,J. C. Lacroixh, S. Aeiyach’, P. C. Lacazeb a LAPOL, Univ. Fed. RS, Port0 Alegre, 90035-190, Brazil ’ ITODYS, Univ. Paris 7 - CNRS, Paris 75005, France
Abstract Polyaniline (PAni) and poly( 1,5diaminonaphthalene) (polyl &DAN) films can be deposited on mild steel from aqueous HC104. This medium allows passivation of the substrate without preventing monomer oxidation. The tihns are uniform, with controlled thickness and exhibit electroactive properties between 0.3 V and 1.0 V SCE w&ich are similar to those of PAni and poly(l,S-DAN) generated on platinum. Electrosynthesisperformed in the presenceof two monomers leads to a composite film which presents excellent adhesion properties on mild steel. Keywords: Polyaniline,
Corrosion
Protection,
Poly(i.5~liami~~onaphtl~al~~e).
1. Introduction We are currently concerned with the synthesis of modified electrodes by electropolymerization of naphthalene derivatives bearing as substituents two fimctional groups, e.g. naphthylamines containing -OH or -NH2 groups on the second of the fused benzene rings. It was demonstrated that in acidic media, electrooxidation occurred selectively via the - NH2 group. The polymer has amine (-NH-C) and imine(-N=C) links behveen naphthalene rings, characteristic of a polyaniline-like structure bearing free OH or NH2 groups on the second nucleus P-41. Since mild steel is the most interesting commodity metal from the technological point of view, the aim of this work is to show the feasibility of the electrosynthesis of poly(l,5-DAN), PAni and composite film, on mild steel from aqueous acid. 2. Experimental Electrochemical studies were carried out in a singlecompartment three-electrode cell, using a EGkG PAR 173/362 potentiostat. The reference was a saturated calomel electrode (SCE) and the auxiliary electrode a Pt sheet. The working electrodes were plates of mild steel (Sollac XC 18). Before electropolymer&ion, they were rinsed in acetone with ultrasonic agitation. For alI CVs we used a scan rate of 50 mVs-’ and the first potential scan is between + 0.32 and +1 IOV. Subsequent scans are paformed in the range between + 0.32 and +0.9oV on mild steel electrodes in aqueous lM HClO4. * 1 rue Guy de la Brosse, 75005, Paris, Frence. Tel. 33-144276961 Code 33 + 144276t714; e-mail: mcpha~oriJ7.iussiev.fi
0379-6779/99/$- seefront PII: SO379-6779(98)01020-O
matter0
1999 Elsevier
Fax: ht
Science
S.A.
All rights
In order to characterizethe films obtained, FTIR spectra were recorded on a Nicolet SX 60 Fourier Transform spectrometer, and XPS spectra were recorded on a Vacuum Generator Escalab MKl, calibrated by assuming a 285 eV binding energy for aromatic and aliphatic carbons. 3. ResulCsand Discussion Cyclic voltamrnetry with a mild steel electrode was carried out in aqueous lM HClO4 in order to determine in which potential region the electrode would be passive. The electrode is activated and dissolved between -0.6 and + 0.6V. Then passivation occurs as ferric oxide is formed. At about 1.2V, transpassivation is reached and oxygen is evolved. In the reverse scan, depassivation is observed when the potential reaches 0.3V [5]. Thus, a passivation window appears ranging between +0.3 and +I .2V; this could allow both polymerization in this range. Typical cyclic voltamograms (CVs) taken during the electrooxidation of 10-l M aniline and lo” M 1&DAN are shown in Fig. 1 and 2, respectively. In both cases,the first scan shows the oxidation of the monomer at 1.05V (aniline) and at 0.74V (1,5-DAN). In the second scan, the redox systemsof the films appears: two redox couples are detected for PAni, couple I at 0.5OV (I&) / 0.45V (E&, couple II at 0.8lV (Ep) / 0.76V (Epc);poly(l,S-DAN) presents only one redox system at 0.48V (Epa) / 0.44V (E&. The current on the cathodic and anodic waves increaseswith time, reflecting the growth of the polymer films. Similar CVs were obtained for poly(l,S-DAN) tihn formed on platinum [3]. The PAni is green, uniform and the film thickness increases with scmning but, at the end, the film becomes powdery. FTIR and XPS analysis show that its structure is very similar to that obtained by Can&et ef al. [6]. reserved.
J.-C. Lacroix
et al. / Synthetic
Metals
102 (1999)
1390-1391
The colour of the poly( 1,5-DAN) film changes from yellow to blue, depending on the mtmber of scans. The film is thin, very adherent to the mild steel electrode and presents a rather compact and uniform morphology, similar to that obtained on Pt and glassycarbon electrodes [31. We have attempted to copolymerke 1,5-DAN and aniline. The CVs obtained with 2.10” M 1,5-DAN and 10-l M aniline in 1M HC104 are presented in Fig. 3.
1391
50pA
Fig. 3. CVs of 10m3M 1,5-DAN + l@’ M aniline in 1M HC104 on a mild steel electrode
I Fig. 1. CVs of 10-l M aniline in 1M HC104 on a mild steel electrode
E w
In the fmt scan, a first oxidation peak is observed at 0.74V corresponding to the oxidation of 1,5-DAN, then a second one at 1.OOV,corresponding to the oxidation of aniline (this peak can not be seen in Fig. 3 becauseof the scale). ln the second scan, a well defined redox system is obtained at 0.48V (Epa) / 0.44V (E& (couple I) and after several scans,a second system appears at 0.79V (I&) IO.75V (I&) (couple II). It seemsthat at the beginning the growth of poly( 1,5-DAN) is predominant owing to a better adsorption of 1,5-DAN onto mild steel as compared to aniline. The redox couple I principally due to poly(l,S-DAN) is observed already in the second potential scan. The redox couple II due to PAni appears only after a few scanswith a relatively weak current wave; after ten minutes, this behaviour is inverted, showing an acceleration in the growth of the secondredox system(PAni). 4. References
Fig. 2. CVs of 10” M 1,5-DAN in 1M HC104 on a mild steel electrode
[l] M.C. Pham, M. Mostefai, M. Simon and P.C. Lacaze, Synth. Met., 63 (1994) 7. [2] M.C. Pham, M. Mostefai, P.C. Lacaze and L.H. Dao, Synth. Met., 68 (1994) 39. [3] M.C. Pham, M. Oulahyane, M. Mostefai and M.M. Chehimi, Spth. Met., 9312(1998) 89. [4] M.C. Pham, B. Piro, M. E.A. Bazzaoui, M. Hedayatullah, JC. Lacroix, P. Novak, 0. Haas., Synth. Met., 92 (1998) 197. [5] A. Meneguzzi, CA. Ferreira, MC. Pham, M. Delamar, P.C. Lacaze, Eletrochim. Acta, accepted for publication. [6] J.L. Camalet, J.C. Lacroix, S. Aeiyach, K. Chane-Ching, P.C. Lacaze, J. Electroanal. Chem. 416 (1996) 179.
Electroactive poly(aromatic amine) films deposited on mild steel A. Meneguzzi”, M. C. Pham”,‘, C. A. Ferreiraa,J. C. Lacroixh, S. Aeiyach’, P. C. Lacazeb a LAPOL, Univ. Fed. RS, Port0 Alegre, 90035-190, Brazil ’ ITODYS, Univ. Paris 7 - CNRS, Paris 75005, France
Abstract Polyaniline (PAni) and poly( 1,5diaminonaphthalene) (polyl &DAN) films can be deposited on mild steel from aqueous HC104. This medium allows passivation of the substrate without preventing monomer oxidation. The tihns are uniform, with controlled thickness and exhibit electroactive properties between 0.3 V and 1.0 V SCE w&ich are similar to those of PAni and poly(l,S-DAN) generated on platinum. Electrosynthesisperformed in the presenceof two monomers leads to a composite film which presents excellent adhesion properties on mild steel. Keywords: Polyaniline,
Corrosion
Protection,
Poly(i.5~liami~~onaphtl~al~~e).
1. Introduction We are currently concerned with the synthesis of modified electrodes by electropolymerization of naphthalene derivatives bearing as substituents two fimctional groups, e.g. naphthylamines containing -OH or -NH2 groups on the second of the fused benzene rings. It was demonstrated that in acidic media, electrooxidation occurred selectively via the - NH2 group. The polymer has amine (-NH-C) and imine(-N=C) links behveen naphthalene rings, characteristic of a polyaniline-like structure bearing free OH or NH2 groups on the second nucleus P-41. Since mild steel is the most interesting commodity metal from the technological point of view, the aim of this work is to show the feasibility of the electrosynthesis of poly(l,5-DAN), PAni and composite film, on mild steel from aqueous acid. 2. Experimental Electrochemical studies were carried out in a singlecompartment three-electrode cell, using a EGkG PAR 173/362 potentiostat. The reference was a saturated calomel electrode (SCE) and the auxiliary electrode a Pt sheet. The working electrodes were plates of mild steel (Sollac XC 18). Before electropolymer&ion, they were rinsed in acetone with ultrasonic agitation. For alI CVs we used a scan rate of 50 mVs-’ and the first potential scan is between + 0.32 and +1 IOV. Subsequent scans are paformed in the range between + 0.32 and +0.9oV on mild steel electrodes in aqueous lM HClO4. * 1 rue Guy de la Brosse, 75005, Paris, Frence. Tel. 33-144276961 Code 33 + 144276t714; e-mail: mcpha~oriJ7.iussiev.fi
0379-6779/99/$- seefront PII: SO379-6779(98)01020-O
matter0
1999 Elsevier
Fax: ht
Science
S.A.
All rights
In order to characterizethe films obtained, FTIR spectra were recorded on a Nicolet SX 60 Fourier Transform spectrometer, and XPS spectra were recorded on a Vacuum Generator Escalab MKl, calibrated by assuming a 285 eV binding energy for aromatic and aliphatic carbons. 3. ResulCsand Discussion Cyclic voltamrnetry with a mild steel electrode was carried out in aqueous lM HClO4 in order to determine in which potential region the electrode would be passive. The electrode is activated and dissolved between -0.6 and + 0.6V. Then passivation occurs as ferric oxide is formed. At about 1.2V, transpassivation is reached and oxygen is evolved. In the reverse scan, depassivation is observed when the potential reaches 0.3V [5]. Thus, a passivation window appears ranging between +0.3 and +I .2V; this could allow both polymerization in this range. Typical cyclic voltamograms (CVs) taken during the electrooxidation of 10-l M aniline and lo” M 1&DAN are shown in Fig. 1 and 2, respectively. In both cases,the first scan shows the oxidation of the monomer at 1.05V (aniline) and at 0.74V (1,5-DAN). In the second scan, the redox systemsof the films appears: two redox couples are detected for PAni, couple I at 0.5OV (I&) / 0.45V (E&, couple II at 0.8lV (Ep) / 0.76V (Epc);poly(l,S-DAN) presents only one redox system at 0.48V (Epa) / 0.44V (E&. The current on the cathodic and anodic waves increaseswith time, reflecting the growth of the polymer films. Similar CVs were obtained for poly(l,S-DAN) tihn formed on platinum [3]. The PAni is green, uniform and the film thickness increases with scmning but, at the end, the film becomes powdery. FTIR and XPS analysis show that its structure is very similar to that obtained by Can&et ef al. [6]. reserved.
J.-C. Lacroix
et al. / Synthetic
Metals
102 (1999)
1390-1391
The colour of the poly( 1,5-DAN) film changes from yellow to blue, depending on the mtmber of scans. The film is thin, very adherent to the mild steel electrode and presents a rather compact and uniform morphology, similar to that obtained on Pt and glassycarbon electrodes [31. We have attempted to copolymerke 1,5-DAN and aniline. The CVs obtained with 2.10” M 1,5-DAN and 10-l M aniline in 1M HC104 are presented in Fig. 3.
1391
50pA
Fig. 3. CVs of 10m3M 1,5-DAN + l@’ M aniline in 1M HC104 on a mild steel electrode
I Fig. 1. CVs of 10-l M aniline in 1M HC104 on a mild steel electrode
E w
In the fmt scan, a first oxidation peak is observed at 0.74V corresponding to the oxidation of 1,5-DAN, then a second one at 1.OOV,corresponding to the oxidation of aniline (this peak can not be seen in Fig. 3 becauseof the scale). ln the second scan, a well defined redox system is obtained at 0.48V (Epa) / 0.44V (E& (couple I) and after several scans,a second system appears at 0.79V (I&) IO.75V (I&) (couple II). It seemsthat at the beginning the growth of poly( 1,5-DAN) is predominant owing to a better adsorption of 1,5-DAN onto mild steel as compared to aniline. The redox couple I principally due to poly(l,S-DAN) is observed already in the second potential scan. The redox couple II due to PAni appears only after a few scanswith a relatively weak current wave; after ten minutes, this behaviour is inverted, showing an acceleration in the growth of the secondredox system(PAni). 4. References
Fig. 2. CVs of 10” M 1,5-DAN in 1M HC104 on a mild steel electrode
[l] M.C. Pham, M. Mostefai, M. Simon and P.C. Lacaze, Synth. Met., 63 (1994) 7. [2] M.C. Pham, M. Mostefai, P.C. Lacaze and L.H. Dao, Synth. Met., 68 (1994) 39. [3] M.C. Pham, M. Oulahyane, M. Mostefai and M.M. Chehimi, Spth. Met., 9312(1998) 89. [4] M.C. Pham, B. Piro, M. E.A. Bazzaoui, M. Hedayatullah, JC. Lacroix, P. Novak, 0. Haas., Synth. Met., 92 (1998) 197. [5] A. Meneguzzi, CA. Ferreira, MC. Pham, M. Delamar, P.C. Lacaze, Eletrochim. Acta, accepted for publication. [6] J.L. Camalet, J.C. Lacroix, S. Aeiyach, K. Chane-Ching, P.C. Lacaze, J. Electroanal. Chem. 416 (1996) 179.