Monitoring of corrosion processes and hydrodynamic flow pattern in oil/brine mixtures of various compositions between 0 and 80% in volume of oil has been investigated by means of electrochemical impedance and noise measurements. In such two-phase electrolytes the electrode behaviour is mostly characterized by the fact that the state of the corroding metallic surface evolves in a highly dynamic way as a result of local heterogeneities yielded by the non-uniform phase distribution near the electrode. This is why conventional electrochemical current and/or potential noise, as well as electrochemical impedance measurements, showed very poor reproducibility and weak sensitivity to electrolyte composition and flow changes. In contrast to conventional techniques, the electrolyte resistance fluctuations have shown to be a highly sensitive and reliable tool conveying real-time information about the two-phase flow pattern and electrolyte composition. Such measurements can be an indirect way to evaluate the environment aggressiveness in industrial plant and field applications. (C) 2004 Elsevier Ltd. All fights reserved.