Zairyo-to-Kankyo
Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
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  • Taro Kono, Yoko Nishida, Naoto Nakazato, Isshiki Kazuki, Yasuo Nakamur ...
    2018 Volume 67 Issue 8 Pages 324-330
    Published: August 15, 2018
    Released: March 20, 2019
    JOURNALS RESTRICTED ACCESS

    In order to clarify the relationship between the anode buried depth and the interference effect in a cathodic protection of impressed current system, evaluation by field tests and the finite element analysis were carried out. Evaluation parameters of the interference effect were the ground surface potential distribution formed by an anode and a cathode, and the internal current in a simulated underground metallic utility. Changes of these parameters were measured and observed by change of the buried depth of the anode. As a result, when protection current was small and the distance between the underground metallic utility and the cathode was 1 m, it showed that interference effect did not depend on anode buried depth.

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  • Kae Amano, Mikako Moriyama, Mikitomo Ikeda, Makoto Hibino, Shigenobu K ...
    2018 Volume 67 Issue 8 Pages 331-335
    Published: August 15, 2018
    Released: March 20, 2019
    JOURNALS RESTRICTED ACCESS

    In this study, the influence of chemical factors of anticorrosion paint blended with blast furnace slag mixed cement on rust prevention effect was evaluated electrochemically. The blast furnace slag mixed cement provides an alkali atmosphere in the rust preventive layer and protects steel from invasion of corrosive agents. The rust preventive effect is emphasized when used in combination with nitrite. As a condition for nitrite to exhibit rust prevention effect, strong alkali and nitrite / chloride concentration ratio of [NO2]/[Cl]≧1 are necessary. Sulfate ions required smaller amount of nitrite ions than chloride ions.

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Research Paper
  • Shuji Nishida, Tomohiro Ishii, Mitsuyuki Fujisawa, Reiko Sugihara
    2018 Volume 67 Issue 8 Pages 336-345
    Published: August 15, 2018
    Released: March 20, 2019
    JOURNALS RESTRICTED ACCESS

    The rusting of stainless steel in an atmospheric environment is mainly caused by dew droplets. However, the dew behaviors such as dew forming and drying that lead to rusting have not been fully clarified yet. In this study, the dew behaviors were precisely analyzed by the in-situ microscopic observation under the atmospheric condition simulating real environment.

    The dew forming process progresses with 2 phenomena: the growth of the single droplet and the coalescence with another one. The mass of the sea salt in a single droplet increases by these phenomena.

    The dew drying process is divided into three stages: the pinning stage when the contact angle of the droplet decreases, the de-pinning stage when the contact area of the droplet decreases, and the self-pinning stage when the contact angle decreases furthermore. At the self-pinning stage, the salt starts to precipitate and the rust forms under and beside the precipitation.

    It is considered that those behaviors of dew forming and drying cause the formation of the rusting pattern on the stainless steel; a number of small rusted points are distributed uniformly.

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