XII Iberian Meeting of Electrochemistry XVI Meeting of the ...

XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society O D 01
Quasi-simultaneous localised measurements of current density
and ion distribution (pH, Cl - , Na + )
Svetlana V. Lamaka 1 , M. G. Taryba 1 , F. Montemor 1 , H. S. Isaacs 2 ,
M. G. S. Ferreira 1,3
1 ICEMS, Instituto Superior Técnico, UTL, Av. Rovisco Pais 1049-001 Lisbon, Portugal
2 Brookhaven National Laboratory, Upton, NY 11973, USA
3 CICECO, Dep.Ceramics and Glass Eng., University of Aveiro, 3810-193, Aveiro, Portugal
sviatlana.lamaka@ist.utl.pt
Scanning vibrating electrode technique (SVET) measures the potential differences
in solution due to the ionic flux produced above the sample surface during
electrochemical corrosion as it flows from anode to cathode. The measured potential
difference is converted to an electrical current density (µA/cm ) at the point of
measurement. SVET is widely used as a powerful electrochemical technique for
corrosion related studies. However, corrosion processes involve not only oxidationreduction
reactions but also acid-base interactions. Acid-base equilibria can be studied
by several localized electrochemical techniques in potentiometric mode, for example
SECM and SIET. The same applies for determination of Cl - that plays a crucial role in
the ionic equilibria at the surface of corroding metals.
Scanning ion-selective electrode technique (SIET) works as a micro-potentiometric
tool allowing measurements of specific ions over the active surface in solution. The size
of the measuring tip of the ion-selective microelectrode is around 2 micron. SIET and
SVET provide valuable and complementary information. Sequential use of both
techniques was demonstrated by several groups in the field of corrosion [1-4].
The presentation will describe SVET and SIET measurements undertaken
simultaneously with a time lag 1.5 to 4 seconds. The combined SVET-SIET
measurements correlate electrochemical oxidation-reduction processes with acid-base
chemical equilibria. Simultaneously rather than sequentially measured distribution of
specific ions and current density provides a higher quality of local data that can be used
for modelling and prediction of corrosion.
Acknowledgments: The support by Fundação para a Ciência e a Tecnologia (F CT, Portugal)
-
LA-2008-214261is gratefully acknowledged.
References
[1] Ding, H.; Hihara, L.H. J.Electrochem.Soc. 2005, 152, B161.
[2] Ogle, K.; Morel, S.; Jacquet, D. J.Electrochem.Soc. 2006, 153, B1.
[3] Lamaka, S.V.; Karavai, O.V.; Bastos, A.C.; Zheludkevich, M.L.; Ferreira, M.G.S.
Electrochem.Commun. 2008, 10, 259.
[4] Bastos, A.C.; Taryba, M.G.; Karavai, O.V.; Zheludkevich, M.L.; Lamaka, S.V.; Ferreira,
M.G.S. Electrochem.Commun. 2010, 12, 394.
September, 811, 2010. ISEL - Lisbon 47