Zairyo-to-Kankyo
Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Volume 70, Issue 10
Displaying 1-6 of 6 articles from this issue
Commentary
Letter to the Editor
Conference Publication
  • Ayumu Minoura, Masanobu Kumagai, Sachi Ikemoto, Yasuko Kitahara, Watar ...
    2021 Volume 70 Issue 10 Pages 318-322
    Published: October 10, 2021
    Released on J-STAGE: November 10, 2021
    JOURNAL FREE ACCESS

    Type 304 stainless steel was tested as a bipolar plate material in a PEFC environment through single cell operation. The cell failed after 430 h operation and it was inspected through surface observation of the bipolar plates by SEM and XPS together with contamination analysis of the gas diffusion layer (GDL) which was in contact with the bipolar plate. Secondary electron images and XPS spectra showed that iron oxides were deposited on the bipolar plate surface at the cathode side. On the other hand, needle like crystals were formed on the anode side. The EPMA analysis of the GDL revealed that iron was the main contaminant at cathode side while every element (Cr, Fe, Ni) was detected at anode side. The results suggested that the stainless steel was in active state at anode side. The GDL at cathode side was contaminated only with iron(III) probably because generated water washed away other ions with higher solubility.

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  • Daiki Katsuno, Takuya Hiramatsu, Makoto Kawamori, Junichiro Kinugasa, ...
    2021 Volume 70 Issue 10 Pages 323-326
    Published: October 10, 2021
    Released on J-STAGE: November 10, 2021
    JOURNAL FREE ACCESS

    High strength steels for automobiles should be concerned about hydrogen embrittlement. Therefore, we investigated the hydrogen embrittlement of 1500 MPa class high strength steel in atmospheric environment in the form of U-bend test piece. Cracks due to hydrogen embrittlement didn’t occur in 36 months of exposure to Choshi and 12 months of exposure to Miyakojima under the conditions of bending radius of 5 mm, 10 mm, 15 mm and stress of 1300 MPa, 1500 MPa. On the other hand, test pieces cracked after 20 months of exposure to Miyakojima. Corrosion test in Miyakojima showed that reduction of the steel thickness due to corrosion reached original test piece thickness after 24 months. Therefore, it is considered that cracks after 20 months of exposure to Miyakojima was mainly caused by corrosion.

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Research Paper
  • Masato Yamashita, Masamitsu Takahashi, Hiroshi Deguchi, Yasunori Hayas ...
    2021 Volume 70 Issue 10 Pages 327-333
    Published: October 10, 2021
    Released on J-STAGE: November 10, 2021
    JOURNAL FREE ACCESS

    The structure of corrosion products and the corrosion behavior of carbon steel coated with a zinc-rich paint containing two metallic compounds, Al2(SO43 and BaO, were studied through a wet and dry cyclic corrosion test. After the corrosion test, a white corrosion product and a red iron rust formed on the surface of the zinc-rich paint coating without the two metallic compounds. In contrast, their formation was suppressed on the surface of the zinc-rich paint coated film containing the two metallic compounds. Moreover, the addition of a small amount of the metallic compounds to the coated film drastically decreased corrosion current density of the coated steel, accompanied with the decrease in corrosion potential. Structural analyses revealed that simonkolleite (Zn5(OH)8Cl2・H2O) containing Al and nano-phase BaSO4 were formed in the zinc-rich paint coating incorporated with the metallic compounds. This novel structure of the corrosion products was considered to improve the protectiveness of the zinc-rich paint coating.

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  • Masahiro Sakai, Tsubasa Kimura, Tomoyoshi Irie, Hiroshi Yakuwa
    2021 Volume 70 Issue 10 Pages 334-339
    Published: October 10, 2021
    Released on J-STAGE: November 10, 2021
    JOURNAL FREE ACCESS

    The C-ring sample was immersed in an ammonia solution containing tetraammine copper ion. The corrosion potential and polarization curve of the sample were measured in order to electrochemically investigate the stress corrosion cracking mechanism of the phosphorus deoxidized copper tube. The phenomenon was observed in which the corrosion potential rapidly increased around 10 hours later. In addition, tarnished film was formed and SCC occurred after rapid increase in corrosion potential. From the potential-pH diagram, it was found that the sample fluctuated from the Cu(NH32+ region to the Cu(OH)2 region during the immersion test. However, it was clarified that SCC did not occur and the sample was dissolved under the solution conditions that were always present in the Cu(NH32+ region.

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