A direct current potential drop method for evaluating oxide film thickness formed in high-temperature water

• ANZAI Hideya

  Quality Assurance Division, Hitachi, Ltd., Power Business Unit

• ISHIBASHI Ryo

  Center for Technology Innovation-Materials, Research and Development Group Hitachi, Ltd.

• SAKA Masumi

  Department of Nanomechanics, Tohoku University

抄録

To establish an evaluation technique for oxide film thickness in-situ, the applicability of a four-point-probe direct current potential drop method is discussed in this study. Several samples of JIS SUS316L stainless steel with different oxide film thickness were prepared after immersing them in oxygenated pure water at 288°C for different periods. The oxide film thickness was measured by cross sectional observation using a transmission electron microscope. Potential drop on the oxide surface was measured every second during an acquisition period of about 20 s while a constant current was being injected into the sample simultaneously. This kind of measurement was repeatedly carried out at several arbitrary contact positions on the surface of the same sample. The measurement results showed that the potential drop slightly changed during the acquisition period and the tendency varied at the different contact positions. Multiple measurements at different contact positions revealed that the tendency could be categorized into two general types: the decreasing potential drop and the increasing potential drop, defined by the overall trend of the potential drop during the acquisition time. It was found that the ratio of contact positions with a decreasing potential drop tendency to all the contact positions of measurement tended to increase as applied current increased. This tendency depended on the oxide film thickness. The threshold value of applied current was found to correlate well with the oxide film thickness when the occurrence rate of decreasing potential drop ranged from 70 to 90% showing the best correlation at 70%.

収録刊行物

• Mechanical Engineering Letters

  Mechanical Engineering Letters 2 (0), 15-00632-15-00632, 2016

  一般社団法人 日本機械学会

キーワード

• Electrical resistivity
• Direct current
• Stainless steels
• Oxidation
• Surface preparation
• Stress corrosion cracking
• High-purity water

詳細情報

• CRID: 1390001205763019264
• NII論文ID: 130005146366
• DOI: 10.1299/mel.15-00632
• ISSN: 21895236
• Web Site: https://www.jstage.jst.go.jp/article/mel/2/0/2_15-00632/_pdf
• 本文言語コード: en
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