Journal of the Electrochemical Society, ( ISI ), No (127), Year (2006-2) , Pages (330-335)

Title : The relationship between pit Chemistry and pit geometry near the critical pitting temperature ( The Relationship Between Pit Chemistry and Pit Geometry Near the Critical Pitting Temperature )

Authors: Mohammad Hadi Moayed , R.C. Newman ,

Citation: BibTeX | EndNote

In pitting corrosion, the pit stability product is the product of anodic current density and depth, ia, which for an open hemispherical cavity would be proportional to the product of the cation diffusivity and some interfacial concentration of the dissolving cations, DC. Many authors believe that pit growth is diffusion-controlled, i.e., C = Cs solubility of the metal salt. Temporarily, prior to salt film precipitation, supersaturation is possible up to some maximum value: C = Css. Estimates of ia for real pits can be used to analyze their degree of occlusion, that is, by how much the effective value of pit radius aeff = nFDCs /i, where  is a geometrical factor close to 0.5 differs from the geometrical pit radius calculated using Faraday’s law a. Small pits are found to be highly occluded, i.e., aeff  a. For metastable pits formed in a high-alloy 904L stainless steel, the value of ia increases linearly with pit depth, and for a temperature 7° below the critical pitting temperature CPT, approaches DCs at the largest observed pit depth of ca. 10 m, but very large metastable pits formed closer to the CPT have ia values that exceed even DCss. We show that this is consistent with the time-dependent development of a dish-shaped pit geometry, and that by suitable correction the stability products become consistent with diffusion-controlled pit growth.

Keywords

, stainless steel, pitting corrosion, critical pitting temperature, pit stability
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@article{paperid:102353,
author = {Moayed, Mohammad Hadi and R.C. Newman},
title = {The relationship between pit Chemistry and pit geometry near the critical pitting temperature},
journal = {Journal of the Electrochemical Society},
year = {2006},
number = {127},
month = {February},
issn = {0013-4651},
pages = {330--335},
numpages = {5},
keywords = {stainless steel; pitting corrosion; critical pitting temperature; pit stability product.},
}

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%0 Journal Article
%T The relationship between pit Chemistry and pit geometry near the critical pitting temperature
%A Moayed, Mohammad Hadi
%A R.C. Newman
%J Journal of the Electrochemical Society
%@ 0013-4651
%D 2006

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