use of svet and secm to study the galvanic corrosion of...

Corrosion Science 49 (2007) 726–739

www.elsevier.com/locate/corsci

Use of SVET and SECM to study the galvaniccorrosion of an iron–zinc cell

A.M. Simoes a,*, A.C. Bastos a, M.G. Ferreira a,b,Y. Gonzalez-Garcıa c, S. Gonzalez c, R.M. Souto c

a ICEMS / Departamento de Engenharia Quımica, Instituto Superior Tecnico, Av. Rovisco Pais,

1049-001 Lisboa, Portugalb Departamento de Engenharia de Ceramica e do Vidro, Universidade de Aveiro,

Campus Universitario de Santiago, 3810-193 Aveiro, Portugalc Departamento de Quımica Fısica, Universidad de La Laguna, E-38200 La Laguna,

Tenerife, Canary Islands, Spain

Received 31 August 2005; accepted 21 April 2006Available online 1 August 2006

Abstract

The work makes use of the scanning vibrating electrode technique (SVET) and the scanning elec-trochemical microscope (SECM) to investigate microscopic aspects of the electrochemical reactionsthat occur in an iron–zinc galvanic couple immersed in aqueous sodium chloride solution. Detectionof the corrosion processes was made by sensing the phenomena occurring in solution. The SVETprovided information on the distribution of ionic currents arising from the metal surface, whereasthe SECM measured the concentration of chemical species relevant to the corrosion processes.The two techniques had comparable sensitivity for the corrosion of iron but significant differenceswere observed concerning the detection of corrosion of zinc.� 2006 Elsevier Ltd. All rights reserved.

Keywords: A. Iron; A. Zinc; B. SVET; B. SECM; C. Galvanic couple

0010-938X/$ - see front matter � 2006 Elsevier Ltd. All rights reserved.

doi:10.1016/j.corsci.2006.04.021

* Corresponding author. Tel.: +351 218417963; fax: +351 218404589.E-mail address: [email protected] (A.M. Simoes).

mailto:[email protected]

A.M. Simoes et al. / Corrosion Science 49 (2007) 726–739 727

1. Introduction

Several micro-chemical and micro-electrochemical techniques have been introduced tothe corrosion laboratory in recent times with the advantage of giving microscopic informa-tion on the processes occurring at the surface of corroding metals. Electrochemical noiseanalysis from immersed microelectrodes [1–6], scanning Kelvin probe investigations [7–14], localised electrochemical impedance spectroscopy [15–18], wire beam electrodes(WBE) [19–23], capillary and droplet cells [24–32] are currently used in a number of labo-ratories to investigate localised corrosion processes with great success. Scanning probetechniques like atomic force microscopy and scanning tunnelling microscopy are alsobecoming increasingly used for these investigations, although the limitations they exhibitfor in situ operation in the case of complex systems such as corroding metals, tend to restricttheir use to either the investigation of highly idealized systems as single crystal probes[33–35] or their later ex situ characterization under air or vacuum operation [36–40].

Special mention should be made of scanning electrochemical techniques with high spa-tial resolution that allow in situ measurements, as they can provide valuable informationon the behaviour of the corroding system at a microscopic level. They consist basically ofscanning a microelectrode over the immersed specimen, either in a static mode (scanningreference electrode technique, SRET) or in a vibrating mode (scanning vibrating electrodetechnique, SVET), allowing for mapping of either current or potential in the solution [41].These techniques have been effective in monitoring the progress of many corrosion situa-tions [42–54]. An alternative technique is the scanning electrochemical microscope(SECM) [55–58]; in the generation/collection mode, the ultramicroelectrode can work asan amperometric sensor of chemical species in solution, allowing the measurement of localdifferences in electrochemical reactivity on the scanned substrate. The SECM has beenapplied to corrosion research in various occasions [59–74].

In this paper we report the results of experiments designed to follow the corrosionprocesses occurring at iron and zinc samples directly exposed to an aqueous environmentcontaining chloride ions, the metals being either isolated or electrically connected as agalvanic couple. No polarization of the samples was performed, thus allowing the systemsto evolve spontaneously as it occurs in naturally driven corrosion processes. Experimentswere conducted by SVET and SECM in naturally aerated electrolyte at ambienttemperature.

2. Experimental

2.1. Chemicals, materials and sample preparation

Experiments were performed on 99.5% pure iron and 99.95% pure zinc, both suppliedas sheet of thickness of 1 mm by Goodfellow Materials Ltd. (Cambridge, UK). The sheetswere cut and mounted into an epoxy resin sleeve, so that only a square area with ca.1 · 1 mm2 formed the testing metal substrate – Fig. 1(a). For the galvanic couple experi-ments two electrodes were embedded in the resin and connected electrically at the back –Fig. 1(b). The mount with the samples was then polished with silicon carbide paper downto 1200 grit, washed thoroughly with Millipore deionised water, dried with acetone andfinally surrounded laterally by sellotape, thus creating a small container for the electrolytesolution. The electrochemical cells for both SVET and SECM were completed with the

1cm

a b

Fig. 1. Schematics of lateral and top views of the metallic samples embedded in an epoxy sleeve: (a) single wire,(b) Fe and Zn electrodes. In (b) the electrical connection was made at the rear of the mould.

728 A.M. Simoes et al. / Corrosion Science 49 (2007) 726–739

inclusion of their corresponding microelectrodes. Testing was carried out in aqueous 0.1M NaCl solution made from analytical grade reagent and Millipore deionised water.The solution was naturally aerated and experiments were conducted at ambienttemperature.

2.2. SVET instrumentation and experimental procedure

The SVET instrumentation was manufactured by Applicable Electronics Inc. (MA,USA) and controlled by dedicated software. Further details can be found in the literature[54,75]. The technique is based upon the measurement of small potential variations in solu-tion, associated to the ionic fluxes that come from oxidation and reduction reactionsoccurring on the active surface [42,43]. The microelectrode had a platinum tip with a dia-meter of 20 lm and vibrated with an amplitude of 20 lm, its main position being locatedat a distance of 200 lm from the sample. A calibration routine converted the measuredpotentials into current density at the corroding surface [41,76].

2.3. SECM instrumentation and experimental procedure

The Scanning Electrochemical Microscope consisted of model CHI900 (CH-Instru-ments, Texas, USA) and operated with a 10 lm diameter platinum disk at the tip of theprobe, an Ag/AgCl/KCl (saturated) reference electrode and a stainless steel counter elec-trode. All potential values are referred to the Ag/AgCl/KCl (saturated) reference elec-trode. This technique, working in the amperometric mode, measures a faradaic currentat the microdisk, while the tip is rastered over the metal sample. Provided the current iscontrolled by diffusion of the electroactive species to the microelectrode, for a species A

in the solution, the limiting current, i1, is given by [56,57]

i1 ¼ 4nFDACAa; ð1Þwhere DA is the diffusion coefficient of the species, CA is its bulk concentration, a is the tipradius, F the Faraday constant and, n the number of electrons consumed or produced in


the reaction. Further details can be found in [73,74]. The currents measured are presentedas current intensity at the probe.

3. Results

3.1. Iron

The main reactions responsible for corrosion of iron in NaCl solution at neutral pH arethe oxidation of iron

Fe! Fe2þ þ 2e� ð2Þand the reduction of dissolved oxygen

O2 þ 2H2Oþ 4e� ! 4OH� ð3Þ

Reaction (2) leads to an upward flow of metal cations above the anodic regions, which aredetected by SVET as positive currents; conversely, in the cathodic regions an upward flowof OH� anions emerges from the surface as a consequence or reaction (3), being detectedby SVET as negative currents. As long as corrosion exists, these reactions are maintainedand so are the existence of the localized positive and negative ionic flows in solution. Atthe same time, the amount of O2 dissolved in solution is lower near the cathodic regionssince it is consumed in those regions following Eq. (3).

In Fig. 2 it is possible to observe how spontaneous corrosion of iron occurred with clearseparation between a large cathode and a small anode. The anodic and cathodic activitieswere usually maintained at the same locations for several hours, although the locationtended to change as the corrosion products started blocking the surface. The cathodicareas were more difficult to sense with the SVET, because they were less localized.

The progress of reactions (2) and (3) can be followed by selecting adequate potentialvalues at the SECM tip. As an example, Fe2+ ions may be detected by setting the tip at+0.60 V. In these conditions the amperometric detection of Fe2+ is under the limiting cur-rent of oxidation to Fe3+, as confirmed by the cyclic voltammogram depicted in Fig. 3(a).A calibration curve was obtained using 0.1 M NaCl solutions with different additions ofFeSO4(NH4)2SO4 Æ 6H2O. Only a small range of concentrations could be used due toexperimental difficulties, but it showed a reasonably good linear correlation between thecurrent measured and the concentration, as given in Fig. 3(b). Extrapolation of the fittedline towards zero concentration does not cross the Y-axis at zero current, which suggeststhat a calibration curve can lead to better estimation of concentration. Applying Eq. (1) tothe measured currents leads to an average diffusion coefficient of 4.4 · 10�9 m2 s�1, whichis slightly higher than the value 0.72 · 10�9 m2 s�1 from the literature [77]. The detectionof dissolved Fe2+ in solution above a corroding iron electrode is shown in Fig. 4(a). Thisdetection was not easy in the freshly prepared surface but became more evident later, afterscratching the layer of corrosion products. Above the scratched area, an excess of Fe2+

ions was measured; the resulting curves for Fe2+ oxidation were asymmetrical and showednarrow spikes randomly distributed upon a broad shoulder that covered the entire lengthof the iron surface.

The dissolved oxygen in solution, which is consumed in reaction (3) was measured inthe same manner as Fe2+, this time by polarizing the tip at �0.70 V. Amperometric scancurves for dissolved O2 are depicted in Fig. 4(b). The curves display a well-defined

Fig. 2. Ionic current mapping (left) and video images (right) of a pure iron electrode during immersion in 0.1 MNaCl at selected exposure times: (a) ca. 5 min, (b) 1 h, and (c) 1 day. Electrode size: � 1 · 1 mm2. Current scalesare given in lA cm�2.

0.2 0.4 0.6 0.8 1.0-2.0×10-10

-1.0×10-10

0.0

1.0×10-10

2.0×10-10

I / A

E / V (Ag AgCl)

a

0 1 2 3 4 5 61.0×10-11

1.5×10-11

2.0×10-11

2.5×10-11

3.0×10-11

I / A

Fe2+ / mM

b

⏐ ⏐ ⏐

Fig. 3. (a) Cyclic voltammogram measured at the SECM tip immersed in a 5 mM solution of FeSO4(NH4)2SO4.6H2O in 0.1M NaCl; scan rate: 10 mV s�1. (b) Calibration curve for Fe2+ measured with the SECMmicroelectrode set at +0.60 V.


0 500 1000 1500 20002.0×10-11

4.0×10-11

6.0×10-11

8.0×10-11

1.0×10-10

1.2×10-10

50 μm

20 μm

40 μm

I / A

X / μm

a

0 500 1000 1500 20000.0

1.0×10-9

2.0×10-9

3.0×10-9

4.0×10-9

200 μm

60 μm

20 μm

40 μm

I / A

X / μm

b

Fig. 4. Amperometric curves for (a) Fe2+ and (b) O2 obtained above the scratched iron surface, when the tippotential was set at + 0.60 and �0.70 V, respectively. Probe heights for each scan are indicated in the graphs.


depletion above the metal surface, resulting from the cathodic reaction occurring on it.The minimum of the curve approaches zero as the distance to the surface decreases. Whenthe scans were made sufficiently close to the surface, a local anode was revealed in the oxy-gen curve by a local small peak that coincides with the highest accumulation of Fe2+. Theoxygen concentration profile was also assessed by scanning the probe vertically and plot-ting the current at the probe as a function of the vertical distance to the metal surface, asdepicted in Fig. 5. Oxygen depletion is observed starting from 1000 lm from the surface.According to Eq. (1), the measured currents can be converted into concentration valuesby introducing the diffusion coefficient of oxygen in the solution. The value of2.01 · 10�9 m2 s�1 for the diffusion coefficient of oxygen in water [77] resulted in the deter-mination of a bulk concentration of 4.38 · 10�4 M, which is greater than the solubility ofoxygen in 0.1 M NaCl of approximately 2.35 · 10�4 M referred in the literature [78]. Thisdifference may be due to the simultaneous reduction of protons at the potential of�0.70 V. Further, polishing of the microelectrode was made by hand, which may result

0 500 1000 1500 20001.0×10

-9

3.0×10-9

5.0×10-9

7.0×10-9

9.0×10-9

I / A

Z / μm

Fig. 5. Oxygen reduction current over the iron sample obtained by approaching the probe to the iron surface withthe microelectrode potential set at �0.70 V.


either in a small tilt or in a rougher surface, and thus to an increased real area of the plat-inum electrode.

3.2. Zinc

The ionic flows above spontaneously corroding zinc – Fig. 6 – showed a clear definitionof one cathode and one anode well before corrosion signs became visible to the naked eye.The anodic activity results from the oxidation of zinc according to

Zn! Zn2þ þ 2e� ð4Þand the cathodic activity is described by Eq. (3). The currents measured were in the samerange as those previously observed for the iron sample. The attack was very localized, withthe development of one pit only above which the anodic currents continuously increasedduring the period of immersion. The cathodic reaction was quite localized during the firsthour of immersion but became more spread over the surface after one day, when corrosionproducts covered the original cathode.

With the SECM, the probe scan curve for oxygen showed a minimum above the zincelectrode (Fig. 7). This minimum was sharper than on iron, due to the more localized

Fig. 6. Ionic current mapping (left) and video images (right) of a pure zinc electrode during immersion in 0.1 MNaCl at selected exposure times: (a) ca. 5 min, (b) 1 h, and (c) 1 day. Electrode size: � 1 · 1 mm2. Current scalesare given in lA cm�2.

0 500 1000 1500 2000 25000.0

1.0×10-6

2.0×10-6

3.0×10-6

4.0×10-6

5.0×10-6

X / μm

I Zn

2+ /

A

5.0×10-1 0

1.0×10-9

1.5×10-9

2.0×10-9

2.5×10-9

IO

2 / A

Fig. 7. Amperometric curves for Zn2+ (——) and O2 (- - - - - -) obtained 50 lm above the zinc surface, with thetip potential set at �1.15 and �0.70 V, respectively. The scan curve for zinc ions was obtained by forced oxidationof the zinc electrode at � 0.83 V.


cathodic activity. Detection of zinc was not possible under the working conditions. Zincbecomes reduced at potentials below the reversible potential for Zn2+/Zn, at ca.�1.00 V. The disadvantage of this method is that it involves deposition of metallic zincon the microelectrode, with the consequent need for cleaning after the experiment. Inorder to confirm the sensitivity of the technique, the zinc electrode was polarized anodi-cally (�0.83 V) and the surface scanned with the microelectrode polarized at �1.15 V.A distinct peak was then observed. This observation apparently contrasts with the resultsfrom Tada et al. [79], who monitored the concentration of Zn2+ over a zinc electrode.Their study, however, involved galvanic corrosion with a significantly larger cathode toanode area ratio, which led to an acceleration of the process comparable to the anodicpolarization.

3.3. Iron–zinc galvanic couple

Fig. 8 shows maps of ionic currents in solution measured at different distances abovethe surface. The cathodic and anodic activities were well separated and located on ironand zinc, respectively, as anticipated in a galvanic couple with zinc oxidizing sacrificiallyand preventing the corrosion of iron. When the electrodes were connected the potentialbecame shifted to about �1.040 V, i.e., slightly more positive than the potential of zincin the same medium (� �1.060 V). At that potential, iron cannot be oxidized (its potentialwhen corroding freely is � �0.750 V) and the main reactions that take place are the oxi-dation of zinc to Zn2+ ions and the reduction of oxygen at the iron surface. As a result ofthe three-dimensional diffusion of ions from the generating surface, the ionic currentsbecome less intense and less localized with increasing distance. This is revealed by thesharp signals measured near the surface, becoming broader and smaller for longer dis-tances, ultimately vanishing at sufficiently high distances. The same can be observed inFig. 9 for line scans obtained at various distances above the surface. It is interesting tonote that the potential field in solution extends to approximately 1 mm from the surface.Above that, only a baseline was obtained, corresponding to the response of the bulksolution.

-2000-10000 10002000

-2000

02000

-60

-40

-20

0

20

40

60

i z/ μ

Acm

-2

X / μm

Y/μ

m

a

-2000-10000 10002000

-2000

02000

-30

-20

-10

0

10

20

30

i z/ μ

Acm

-2

X / μm

Y/μ

m

b

-2000-10000 10002000

-2000

02000

-10

-5

0

5

10

i z/ μ

Acm

-2

X / μm

Y/μ

m

c-2000-10000 10002000

-2000

02000

-4

-2

0

2

4

i z/ μ

Acm

-2

X / μm

Y/ μ

m

d

Fig. 8. Ionic current mapping of a galvanic couple (pure Fe and pure Zn) in 0.1 M NaCl obtained at variousdistances from the surface: (a) 100 lm, (b) 300 lm, (c) 700 lm and (d) 2000 lm.

-2000 -1000 0 1000 2000

-40

-30

-20

-10

0

10

20

30

40

20001000

700

500

300200

100

20001000

700500

300

200

100

curr

ent /

μA

cm

-2

x distance / μm

Fe Zn

Fig. 9. Ionic current lines obtained at different distances (indicated in lm) above the galvanic couple immersed in0.1 M NaCl.


Fig. 10 shows currents of O2 reduction measured at different heights above the ironelectrode. The amount of oxygen dissolved in solution decreases when approaching theiron surface in either direction, as a result of its consumption in the cathodic reaction.The values encountered are smaller than those obtained for isolated iron and zinc, dueto the enhanced cathodic activity at the iron electrode caused by galvanic coupling.

0 500 1000 1500 2000 25000.0

5.0x10-10

1.0x10-9

1.5x10-9

2.0x10-9

2.5x10-9

1000

500

200

100

I / A

X / μm

Fig. 10. SECM line scans of oxygen reduction current measured in solution above the cathode (Fe) of the Fe–Zngalvanic couple. Heights in microns indicated in the graph.


4. Discussion

The SVET measurements showed that currents fade away with distance from the ions’sources, as expected for processes controlled by diffusion. Fig. 11 plots the absolute peakvalues of both cathodic and anodic currents against probe height. The magnitudes are sim-ilar for the same distance, as anticipated for a galvanic couple where cathodic and anodicactivity should cancel out. It is usually accepted that the currents detected by SVET comefrom the activities on the surface. However, the possibility of other ions, namely Na+ andCl�, migrating to compensate the excess of charges in cathodic and anodic sites, thus giv-ing an increased signal, cannot be totally discarded. In this case the values relative to OH�

and Zn2+ would be overestimated. Work is needed in this particular area to identify thespecies that are in fact giving the SVET response.

The distribution of dissolved oxygen at any height z and radial distance r from the sur-face of a disk-shaped cathode of radius b can be estimated [80] starting from the saturationconcentration C0

O2,

CO2¼ C0

O21� 2

psin�1 2bffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

ðr � bÞ2 þ z2

qþ

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiðr þ bÞ2 þ z2

q0B@

1CA

264

375 ð5Þ

Fig. 12 shows the concentration profiles of O2 obtained using Eq. (1) for the currents mea-sured above Fe either isolated or in the galvanic couple. Also shown is the calculated pro-file using Eq. (5) for the case of Fe in the galvanic couple and the saturation oxygenconcentration in 0.1 M NaCl solution [78]. Since the total height of solution used in theexperiments was only 4–5 mm, Eq. (5) is not totally valid because the concentrationgradient extends all across the liquid layer.

A more complete approach to the corrosion process would include pH, Na+ and Cl�

(ions from the electrolyte) determination as well as improved detection of both Fe2+

0 500 1000 1500 20000

5

10

15

20

25

30

35

curr

ent /

μA

cm

-2

Z / μm

Fe

Zn

⏐⏐

Fig. 11. Absolute values of the cathodic and anodic current density peaks measured by the SVET above theFe–Zn galvanic couple at different heights.

0 1000 2000 3000 40000

1

2

3

4 iron (free) iron (in galvanic pair) equation (5)

|O2|

/ 10

-4 M

height /μm

Fig. 12. Dissolved oxygen in solution above the iron electrode either isolated (solid line) or as cathode of a Fe–Zngalvanic couple (squares), calculated using Eq. (1). The dashed line is the application of Eq. (5) for the Fe–Zncathode using the oxygen saturation concentration in 0.1 M NaCl taken from [78].


and Zn2+. Ultimately, accurate determination of all these species with proper spatial res-olution would lead to the establishment of a model capable of relating the distribution ofthe species in solution and the reactions occurring on the metal surface.

One factor that affects the measurements in both techniques is the stirring of the solu-tion provoked by the movement of the probe. In both techniques, the maximum distanceat which the corrosion process was detected was approximately 1 mm. This distance is


comparable to the total height of electrolyte used (4–5 mm) and therefore the gradients ofpotential and of concentration can be affected by the interface with the atmosphere.

Comparison of the results from the two techniques shows that on iron the detection ofboth the anodic and the cathodic activities were easily detected by both techniques. Whenthe galvanic couple was established, however, the SVET proved to be more sensitive to theanodic currents on zinc, whereas the SECM had a lower sensitivity to the presence of Zn2+

ions in solution. An important advantage of the SECM is the proximity of the probe to themetal surface, which allowed a very good spatial resolution, as was observed in the corro-sion of the single iron electrode.

5. Conclusions

The SVET and the SECM provided consistent information on the local ionic fluxes andlocal concentrations of reagents and products of the electrochemical reactions that occuron the surface. The two techniques offer complementary information: ionic fluxes corre-sponding to cathodic and anodic reactions were measured with the SVET, though it lackedchemical discrimination to identify the nature of the ionic species involved; on the otherhand, by adequately selecting the potential value at the microelectrode in the SECM, reac-tants and products of the corrosion reactions could be identified. Furthermore, their con-centrations in the aqueous phase could be estimated, thus providing in situ information asa function of the time elapsed since immersion.

The results have shown an advantage of the SECM resulting from the proximity of theprobe to the substrate, whereas the SVET proved to be more sensitive to the anodic activ-ity of zinc.

Acknowledgements

The exchange of scientists was supported by a Collaborative Research Programme be-tween Spain (Project No. HP2002-055) and Portugal (Project No. E-53-03). University ofLa Laguna acknowledges the financial support by the Ministerio de Ciencia y Tecnologıa(Madrid, Spain) in the framework of Project CTQ2004-04425/BQU as well as a researchfellowship granted by Cajacanarias to Y.G.-G.

References

[1] C. Gabrielli, F. Huet, M. Keddam, R. Oltra, in: H. Isaacs, U. Bertocci, J. Kruger, S. Smialowska (Eds.),Advances in Localized Corrosion, NACE, Houston, 1990, p. 93.

[2] P.P. Roberge, J. Appl. Electrochem. 23 (1993) 1223.[3] R. Cottis, in: K.R. Trethewey, P.R. Roberge (Eds.), Modelling Aqueous Corrosion. From Individual Pits to

System Management, Kluwer, Dordrecht, 1994, p. 369.[4] F. Mansfeld, L.T. Han, C.C. Lee, C. Chen, G. Zhang, H. Xiao, Corros. Sci. 39 (1997) 255.[5] T. Suter, H. Bohni, Proc. Electrochem. Soc. 95-15 (1995) 127.[6] R.M. Souto, G.T. Burstein, Mater. Sci. Forum 289–292 (1998) 799.[7] M. Stratmann, H. Streckel, Corros. Sci. 30 (1990) 681.[8] M. Stratmann, R. Feser, A. Leng, Electrochim. Acta 39 (1994) 1207.[9] A. Leng, H. Streckel, M. Stratmann, Corros. Sci. 41 (1999) 547.

[10] G. Williams, N. McMurray, J. Electrochem. Soc. 148 (2001) 377.[11] M. Rohwerder, E. Hornung, M. Stratmann, Electrochim. Acta 48 (2003) 1235.[12] J.H.W. de Wit, Electrochim. Acta 49 (2004) 2841.


[13] A.P. Nazarov, D. Thierry, Electrochim. Acta 49 (2004) 2955.[14] B. Reddy, M.J. Doherty, J.M. Sykes, Electrochim. Acta 49 (2004) 2965.[15] R.S. Lillard, J. Kruger, W.S. Tait, P.J. Moran, Corrosion 51 (1995) 251.[16] F. Zou, D. Thierry, Electrochim. Acta 42 (1997) 3293.[17] F. Zou, D. Thierry, H.S. Isaacs, J. Electrochem. Soc. 144 (1997) 1957.[18] S.R. Taylor, Prog. Org. Coat. 43 (2001) 141.[19] Y.-J. Tan, Corrosion 50 (1994) 266.[20] Y.-J. Tan, Corrosion 54 (1998) 403.[21] Y.-J. Tan, Y. Shiti, Prog. Org. Coat. 19 (1991) 89.[22] Y.-J. Tan, Y. Shiti, Prog. Org. Coat. 19 (1991) 257.[23] Z. Quingdong, Z. Zhao, Corros. Sci. 44 (2002) 2777.[24] H. Bohni, T. Suter, A. Schreyer, Electrochim. Acta 40 (1995) 1361.[25] A.W. Hassel, M.M. Lohrengel, Electrochim. Acta 42 (1997) 3327.[26] T. Suter, H. Bohni, Electrochim. Acta 42 (1997) 3275–3280.[27] M.M. Lohrengel, A. Moehring, M. Pilaski, Fresenius J. Anal. Chem. 367 (2000) 334.[28] J.W. Schultze, V. Tsakova, Electrochim. Acta 44 (1999) 3605.[29] A. Vogel, J.W. Schultze, Electrochim. Acta 44 (1999) 3751.[30] T. Suter, H. Bohni, Electrochim. Acta 47 (2001) 191.[31] M.M. Lohrengel, C. Rosenkranz, I. Kluppel, A. Moehring, H. Bettermann, B. Van den Bossche, J.

Deconinck, Electrochim. Acta 49 (2004) 2863.[32] C.J. Park, M.M. Lorenghel, T. Hamelmann, M. Pilaski, Electrochim. Acta 47 (2002) 3395.[33] P. Marcus, V. Maurice, Mater. Sci. Forum 192–194 (1995) 765.[34] P. Marcus, Electrochim. Acta 43 (1998) 109.[35] V. Maurice, W.P. Yang, P. Marcus, J. Electrochem. Soc. 145 (1998) 909.[36] S.J. Chen, F. Sanz, D.F. Ogletree, V.M. Hallmark, T.M. Devine, M. Salmeron, Surf. Sci. 292 (1993) 289.[37] P. Perez-Murano, X. Aymerich, P. Gorostiza, J. Servat, F. Sanz, J. Appl. Phys. 78 (1995) 6797.[38] S.G. Aziz, M.E. Vela, G. Andreasen, R.C. Salvarezza, A. Hernandez Creus, A.J. Arvia, Phys. Rev. B 56

(1997) 4166.[39] M.R. Vogt, A. Lachenwitzer, O.M. Magnussen, R.J. Behm, Surf. Sci. 399 (1998) 49.[40] M.R. VanLandingham, T. Nguyen, W.E. Bird, J.W. Martin, J. Coatings Technol. 73 (923) (2001) 43.[41] H.S. Isaacs, Y. Ishikawa, in: R. Baboian (Ed.), Electrochemical Techniques for Corrosion Engineering,

NACE, Houston, 1986, p. 17.[42] H.S. Isaacs, Corrosion 43 (1987) 594.[43] H.S. Isaacs, J. Electrochem. Soc. 138 (1991) 723.[44] H.S. Isaacs, A.J. Aldykiewicz Jr., D. Thierry, T.C. Simpson, Corrosion 52 (1996) 163.[45] F. Zou, C. Barreau, R. Hellouin, D. Quantin, D. Thierry, Mater. Sci. Forum 289–292 (1998) 83.[46] I.M. Zin, R.L. Howard, S.J. Badger, J.D. Scantlebury, S.B. Lyon, Prog. Org. Coat. 33 (1998) 203.[47] J. He, V.J. Gelling, D.E. Tallman, G.P. Bierwagen, J. Electrochem. Soc. 147 (2000) 3661.[48] F.J. Maile, T. Schauer, C.D. Eisenbach, Prog. Org. Coat. 38 (2000) 117.[49] K. Ogle, V. Baudu, L. Garrigues, X. Philippe, J. Electrochem. Soc. 147 (2000) 3654.[50] S. Bohm, H.N. McMurray, S.M. Powell, D.A. Worsley, Electrochim. Acta 45 (2000) 2165.[51] M. Khobaib, A. Rensi, T. Matakis, M.S. Donley, Prog. Org. Coat. 41 (2001) 266.[52] D.A. Worsley, D. Williams, J.S.G. Ling, Corros. Sci. 43 (2001) 2335.[53] H. Krawiec, V. Vignal, R. Oltra, Electrochem. Commun. 6 (2004) 655.[54] A.C. Bastos, M.G.S. Ferreira, A.M. Simoes, Prog. Org.Coat. 52 (2005) 339–350.[55] R.C. Engstrom, M. Weber, D.J. Wunder, B. Burgess, S. Winquist, Anal. Chem. 60 (1988) 652.[56] A.J. Bard, M.V. Mirkin, in: A.J. Bard (Ed.), Electroanalytical Chemistry, Vol. 18, Marcel Dekker, New

York, 1993, p. 243.[57] A.J. Bard, F.-R. Fan, M.V. Mirkin, in: I. Rubinstein (Ed.), Physical Electrochemistry: Principles, Methods

and Applications, Marcel Dekker, New York, 1995, p. 209.[58] B.R. Horrocks, in: A.J. Bard, M. Stratmann, P.R. Unwin (Eds.), Encyclopedia of Electrochemistry, Vol. 3,

VCH, Weinheim, 2003, p. 444.[59] N. Casillas, S.J. Charlebois, W.H. Smyrl, H.S. White, J. Electrochem. Soc. 140 (1993) L142.[60] N. Casillas, S.J. Charlebois, W.H. Smyrl, H.S. White, J. Electrochem. Soc. 141 (1994) 636.[61] Y. Zhu, D.E. Williams, J. Electrochem. Soc. 144 (1997) L43.[62] D.E. Williams, T.F. Mohiuddin, Y.Y. Zhu, J. Electrochem. Soc. 145 (1998) 2664.


[63] L.F. Garfias-Mesias, M. Alodan, P.I. James, W.H. Smyrl, J. Electrochem. Soc. 145 (1998) 2005.[64] S.B. Basame, H.S. White, Langmuir 15 (1999) 819.[65] S.B. Basame, H.S. White, J. Electrochem. Soc. 147 (2000) 1376.[66] K. Fushimi, M. Seo, J. Electrochem. Soc. 148 (2001) B450.[67] I. Serebrennikova, H.S. White, J. Electrochem. Soc. 4 (2001) B4.[68] K. Fushimi, T. Okawa, K. Azumi, M. Seo, J. Electrochem. Soc. 147 (2000) 524.[69] R.M. Souto, Y. Gonzalez-Garcıa, S. Gonzalez, G.T. Burstein, Corros. Sci. 46 (2004) 2621.[70] D.O. Wipf, Colloid. Surf. A93 (1994) 251.[71] K. Fushimi, M. Seo, Electrochim. Acta 47 (2001) 121.[72] Y. Gonzalez-Garcıa, G.T. Burstein, S. Gonzalez, R.M. Souto, Electrochem. Commun. 6 (2004) 637.[73] A.C. Bastos, A.M. Simoes, S. Gonzalez, Y. Gonzalez-Garcıa, R.M. Souto, Prog. Org. Coat. 53 (2005) 177–

182.[74] A.C. Bastos, A.M. Simoes, S. Gonzalez, Y. Gonzalez-Garcıa, R.M. Souto, Electrochem. Commun. 6 (2004)

1212.[75] A.C. Bastos, A.M. Simoes, M.G. Ferreira, Portugaliae Electrochim. Acta 21 (2003) 371–387.[76] C. Sheffey, in: A.R. Liss (Ed.), Ionic Currents in Development, A.R. Liss Inc., New York, 1986, p. xxv.[77] David R. Lide (Ed.), Handbook of Chemistry and Physics, 84th ed., CRC Press, Boca Raton, Florida, 2003.[78] M.L. Hitchman, Measurement of Dissolved Oxygen, J. Wiley&Sons, New York, 1978, p. 22.[79] E. Tada, S. Satoh, H. Kaneko, Electrochim. Acta 49 (2004) 2279.[80] I. Fatt, Polarographic Oxygen Sensors, CRC Press, Cleveland, Ohio, 1976, p. 13.

use of svet and secm to study the galvanic corrosion of...

Documents