Corrosion current fluctuations at metastable to stable pitting transition of aluminum

Pitting corrosion in aluminum alloys is investigated at open-circuit potential using a three-electrode electrochemical setup which allows simultaneous recordings of potential and current fluctuations. Depending on the electrolyte pH, various fluctuation regimes are revealed and transitions between these regimes are investigated. Random and/or deterministic features of the recorded time series are assessed and a simplified model for pit stabilization is proposed. This model fairly predicts the effect of pH and shows that close to the critical pH for active-passive transition, periodic then chaotic features of the current signals are expected as observed experimentally. The transition between the different regimes occurs either through the period doubling cascade or intermittency mechanisms. Implications for the transition between metastable and stable pits are delineated. (c) 2006 The Electrochemical Society.