The mass transfer given by an electrochemical reaction towards a rotating disk in a solution of surfactant having drag-reducing abilities exhibits a first order transition. Beyond this transition marked by a significant drop of the mass transfer rate, the flow becomes unsteady and is characterized by a hysteresis cycle. This phenomenon was earlier observed for viscoelastic dilute solutions of linear polymers of high molecular weight and is induced by the elongational strain prevailing in the flow around a rotating disk. Spectrum analysis of the fluctuations of both the current, which is related to the mass transfer rate, and the electrolyte resistance (R-e), have been recorded on a disk electrode or on a microelectrode for surfactant solutions. The presence of R-e fluctuations was analyzed in terms of differences in the electrical conductivity of the micellar and monomeric species, thus giving evidence for micelles mechanical degradation and recombination. (C) 2004 Elsevier B.V. All rights reserved.