Please cite this article in press as: O. Dolgikh, et al., Simulation of the role of vibration on Scanning Vibrating Electrode Technique measurements close to a disc in plane, Electrochim. Acta (2016), http://dx.doi.org/10.1016/j.electacta.2016.01.188 ARTICLE IN PRESS G Model EA-26570; No. of Pages 9 Electrochimica Acta xxx (2016) xxx–xxx Contents lists available at ScienceDirect Electrochimica Acta j ourna l ho me page: www.elsevier.com/locate/electacta Simulation of the role of vibration on Scanning Vibrating Electrode Technique measurements close to a disc in plane Olga Dolgikh a , Andrei–Stefan Demeter a,b,∗ , Sviatlana V. Lamaka c,d , Maryna Taryba c , Alexandre C. Bastos e , Marcela C. Quevedo e , Johan Deconinck a a Vrije Universiteit Brussel, Research Group Electrochemical and Surface Engineering, Pleinlaan 2, 1050 Brussels, Belgium b Technical University of Cluj Napoca, Faculty of Electrical Engineering, 26-28 George Baritiu Street, 400027 Cluj Napoca, Romania c Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa. Av. Rovisco Pais, 1049-001 Lisbon, Portugal d MagIC, Magnesium Innovation Centre, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502, Germany e University of Aveiro, CICECO, Department of Materials and Ceramic Engineering, 3810-193 Aveiro, Portugal a r t i c l e i n f o Article history: Received 1 October 2015 Received in revised form 24 January 2016 Accepted 25 January 2016 Available online xxx Keywords: SVET Local mixing numerical simulations multi-ion model concentration gradients a b s t r a c t An elegant and accessible way to account for the local stirring created by the vibration of the SVET tip by adding a new diffusion–like term into the molar flux expression is proposed, in order to avoid solving the fluid flow. This term is maximal in the point of vibration and rapidly decreases with the distance. It is shown that the local mixing leads to a substantial increase of the migration current density in the vicinity of the probe with simultaneous decrease of the diffusion current contribution. This local mixing has no effect on the pH distribution, regardless the applied polarization, and increases under cathodic polarization the oxygen concentration only when the probe is close to the electrode surface which is confirmed by experimental observations. The proposed model is compared with the analytical current density distributions obtained from potential model and experimental data. All this indicates that local mixing might explain why the SVET technique, although based on the measurement of an ohmic current density, measures always the total current density. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Scanning Vibrating Electrode Technique (SVET) has become a widely used investigation technique in the field of corrosion [1–6]. It is used primarily for visualization of the corrosion process pro- gression in terms of anodic and cathodic areas localization and evolution in time, as well as current magnitude monitoring. An ideal analytical tool should not disturb the system under investigation. In practice, the local stirring of the electrolyte is a feature of SVET. This stirring was observed since the introduction of the modern vibrating probe [7]. The main effect of the stirring is the local mixing of the electrolyte, canceling out the concentration gradients. Even at small vibration amplitude (about one diameter of the SVET tip) and moderate vibration frequency, the mixing effect spreads over an area of few times the vibration amplitude. The reduction of the local concentration gradients increases the local ∗ Corresponding author. E-mail addresses: Olga.Dolgikh@vub.ac.be (O. Dolgikh), andrei.demeter@et.utcluj.ro (A. Demeter), sviatlana.lamaka@hgz.de (S.V. Lamaka), mgtaryba@gmail.com (M. Taryba), acbastos@ua.pt (A.C. Bastos), marcelacitlalimreyes@ua.pt (M.C. Quevedo), Johan.Deconinck@vub.ac.be (J. Deconinck). electrical potential gradient [8,9]. On the other hand, larger values of the vibration amplitude lead to important increase in the rates of the electrode reactions taking place under diffusion control, e.g the oxygen reduction reaction on cathode [10]. A deeper investiga- tion of this phenomenon performed by one of the authors, proved that in normal operating conditions (SVET tip of diameter 10–20m placed at more than 50 m above the surface of the sample, vibra- tion amplitude of the same order of magnitude as the tip radius and up to 200 Hz vibration frequency [11,12]) most of the stirring of the electrolyte solution is caused by the movement of the probe dur- ing scanning and less than 5% of the total increase of the cathodic current is caused by the vibration of the tip of the SVET probe [13]. Despite of these disturbances, the technique was experimentally validated long time ago and used to produce valuable analytical results ever since H. Isaacs has adapted SVET for corrosion research [14]. The technique is based on a simple idea: the electrolyte poten- tial in the solution is measured at two different points and then converted to a local current density in the solution, using Eq. (1)  j loc = - U  r ≈ -  ∇U, (1) http://dx.doi.org/10.1016/j.electacta.2016.01.188 0013-4686/© 2016 Elsevier Ltd. All rights reserved.