Zairyo-to-Kankyo
Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Volume 71, Issue 10
Displaying 1-4 of 4 articles from this issue
Commentary
Conference Publication
  • Hidekazu Tanaka, Sami Yamamoto, Tatsuo Ishikawa, Takenori Nakayama
    2022 Volume 71 Issue 10 Pages 279-283
    Published: October 10, 2022
    Released on J-STAGE: November 26, 2022
    JOURNAL FREE ACCESS

    To simulate the atmospheric corrosion of galvanized steels in salinity environment, artificial zinc rust particles were prepared by repeating wet-dry cycle of aqueous ZnCl2 solutions in the presence of zinc rusts such as ZnO and Hydrozincite (Zn5(OH)6(CO32: HZ), and the transformation behavior of added ZnO and HZ into zinc hydroxychloride (Zn5(OH)8Cl2・H2O: ZHC) was examined. The procedure constitutes one cycle of wetting(20℃ and 4 h) and drying (85℃ and 20 h). After 1 cycle, almost all the added ZnO and HZ were transformed into ZHC and its transformation rate was in the order of ZnO>HZ. Increasing the wet-dry cycles enhanced the crystallization and particle growth of ZHC and turned the irregular-shaped ZHC particles into plate-like ZHC ones. These results allow us to infer that initial zinc rusts such as ZnO and HZ generated on the galvanized steels by atmospheric corrosion in salinity environment at initial corrosion stage are immediately transformed into plate-like ZHC rust particles, which form a dense protective rust layer on the steels to enhance the corrosion resistance.

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  • Yuki Yokoyama, Kotaro Doi, Sachiko Hiromoto
    2022 Volume 71 Issue 10 Pages 284-287
    Published: October 10, 2022
    Released on J-STAGE: November 26, 2022
    JOURNAL FREE ACCESS

    This study investigated the influence of the drying condition of the mortar specimens and the CO2 partial pressure during accelerated carbonation tests on the carbonation. The results show that when the change of the specimen’s mass due to drying was large and the CO2 partial pressure was high, the carbonation progress increased. Following the accelerated carbonation test, hyperbaric-oxygen accelerated corrosion tests were conducted. As a result, the steel embedded in the mortar specimens was corroded when the carbonation depth was almost the same as the mortar cover.

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  • Ayumu Minoura, Masanobu Kumagai, Takuji Ube, Hitoshi Yashiro, Masatsug ...
    2022 Volume 71 Issue 10 Pages 288-291
    Published: October 10, 2022
    Released on J-STAGE: November 26, 2022
    JOURNAL FREE ACCESS

    Corrosion resistance and interfacial contact resistance (ICR) of titanium (Ti) bipolar plates for polymer electrolyte menbrane water electrolysis (PEMWE) with different Au plating thickness were evaluated by potentiostatic polarization in a sulfuric acid solution of pH 3.0. No dissolution of Ti was detected by the ICP-MS analysis (<1μg dm-3) when the Au plating thickness was 0.3μm or more. In the case of Ti with Au plating thickness of 0.1μm, Ti dissolved in the plating defects which were confirmed by ULV-SEM observation. The ICR increased after polarization test for Ti without plating, but not for Au plated Ti even with thickness of 0.1μm. These results indicate that microdefects in the plating layer can be starting points of dissolution of substrate, but do not immediately affect the increase in ICR as far as most of the surface remains covered.

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