A Framework for Pitting Corrosion Based on Pit Growth Stability

Gerald S. Frankel

Fontana Corrosion Center, The Ohio State University, USA

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Abstract

This talk will describe a unifying framework for pitting corrosion based on pit growth stability that was recently published in a series of papers. A key new concept in the framework is the maximum pit dissolution current density, i_diss,max, which describes the capacity of pit dissolution for given conditions. Comparison of i_diss,max with the critical diffusion current densities associated with pit repassivation and salt film formation generates new insights to interpret previous observations in a self-consistent way. A mathematical framework describing the behavior of a salt film in a pit and the role of salt films in pit growth will be presented. A novel cryo-based approach for FIB/SEM analysis of the salt film in a pit provides high resolution images that support the model. The framework allows for clear descriptions of the conditions determining the critical pitting temperature, pitting potential and repassivation potential, as well as the influence of alloying effects in stainless steels.