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Home  >  Journal list  >  Journal of the Society of Materials Science, Japan  >  Vol.57  No.11 (2008)  >  pp.1097-1100

Journal of the Society of Materials Science, Japan
<<Previous article Vol.57  No.11 (2008)   pp.1097 - 1100 Next article>>

Extreme-Value Distribution of the Metastable-Pit Depth Estimated by Potential Noise Method

Hiroyuki INOUE1), Riki MORIYA2) and Rokuro NISHIMURA1)
1) Graduate School of Eng. Osaka Pref. Univ.
2) Osaka Pref. Univ.


The extreme-value distribution of metastable-pit depths on SUS304 stainless-steel electrodes was examined. The electrode with the surface area of 10mm2 was immersed in a 10mass% NaCl solution at 60, 70 or 80°C, and measured its potential noises for 48hours. The depth of the metastable pits was calculated from the electric quantity of the local anodic currents that were estimated from the measured potential noises by using the RPS method, assuming the shape of the metastable pits as true hemispheres. The maximum pit depths for 7 to 8 samples at 70 and 80°C were fairly approximated to a Gumbel distribution. The minimum surface area required for forming the stable pit was estimated about 10000mm2, under the conditions employed in this study. From the return period equivalent to this surface area, the critical pit depths at 70 and 80°C were estimated 6.4 and 9.4μm, respectively.


Keyword:
Electrochemical noise analysis, ENA, Pitting, Monitoring, Extreme-value statistic, EVAN, Critical pit radius

Received: March 12, 2008
Published online: November 20, 2008
Copyright (c) 2008 by The Society of Materials Science, Japan

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