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Two-Layer Formation of Passivating Films on Cobalt in Neutral Solution

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J.Electrochem.Soc.128,2522-2528(1981), Two-layer formation of --- cobalt.pdf708.36 kBPDFView/Open
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Title: Two-Layer Formation of Passivating Films on Cobalt in Neutral Solution
Authors: Ohtsuka, Toshiaki Browse this author →KAKEN DB
Sato, Norio Browse this author
Keywords: passivation
chemical analysis
Issue Date: Dec-1981
Publisher: The Electrochemical Society
Journal Title: J. Electrochemical Society
Volume: 128
Issue: 12
Start Page: 2522
End Page: 2528
Publisher DOI: 10.1149/1.2127284
Abstract: Layer structure and thickness of passivation oxide films on cobalt have been investigated at stationary and transient states in solution of 0.30 mol dm^−3 boric acid‐0.075 mol dm^−3 sodium borate mixture of pH 8.4 by means of chemical analysis and in situ ellipsometry combined with electrochemical measurements. A two‐layer structure composed of an inner CoO and an outer CO3ΔO4 is found in a potential range more positive than 0.75V (vs.the hydrogen electrode at the same solution). The nonstoichiometry changes from Δ=0 to 0.33 with increasing anodic potential. The outer CoΔO4 layer thickness increases linearly with potential, whereas the inner layer thickness is not a simple function of potential, but depends on the film formation procedure. A step‐wise potential increase gives an initial rapid growth of the outer Co3ΔO4 layer followed by a gradual thickening of the inner CoO layer. The transient film growth behavior is interpreted in terms of a field‐assisted ion diffusion mechanism, and the self‐diffusion coefficient in the inner CoO layer is estimated to be D/cm sec^-1 = 6.5 X 10^-21~2.6×10^-20.
Rights: © The Electrochemical Society, Inc. 1981. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in J. Electrochem. Soc. 1981 volume 128, issue 12, 2522-2528 .
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 大塚 俊明

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