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Abstract

Stainless steels undergo a sharp rise in pitting corrosion rate as the potential, solution concentration or temperature is changed only slightly. We report experiments using real-time microscopic in situ visualizations that resolve the nucleation and evolution of individual pits during the transition. They suggest that the sudden corrosion onset is explained by an explosive autocatalytic growth in the number of metastable pits and that stabilization of individual pits takes place only later. This finding agrees with a theoretical approach treating the onset of pitting corrosion as a cooperative critical phenomenon resulting from interactions among metastable pits and extends perspectives on control and prevention of the corrosion onset.