Aplicações Especiais da Técnica de SVET

The applicability and limitations of the scanning vibrating microelectrode technique first used on the study of corrosion by Isaacs [1] are reviewed. Source of errors and their influence on the current density maps (i-maps) are analyzed. The influence of the microelectrode size, vibration amplitude and movement [2], distance between working electrode surface and microelectrode tip [3], as well as that of the acquisition time [4] on the determined i values and lateral resolution of the i-map are evaluated, theoretically and experimentally. Results of special applications, as the use of SVET under simultaneous polarization [5] and straining are presented. Quasistationary local potentiodynamic voltammograms obtained from SVET experiments under simultaneous polarization show a very good correlation with actual global voltammograms and a high collecting efficiency when the distance between working electrode surface and microelectrode tip is as small as 30 μm. Additionally, i-maps obtained immediately after straining of Zn-Al coatings on steels, show a difference if straining is performed under dry or wet conditions. From integrated current density values, critical straining values for the onset of localized corrosion could be defined.