Zairyo-to-Kankyo
Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Volume 60 , Issue 9
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  • Takafumi Motooka, Masahiro Yamamoto
    2011 Volume 60 Issue 9 Pages 394-401
    Published: September 15, 2011
    Released: February 22, 2012
    JOURNALS FREE ACCESS
    Corrosion behaviors of metal applicable as nuclear energy and bio-material were investigated in sodium hydroxide solutions. Tested materials were zirconium, titanium, tantalum and niobium. They were immersed in 0.1 to 6.1 mol/dm3 sodium hydroxide solutions for 48 h, and then weight loss measurement, XRD and XPS analyses were conducted. Potentiodynamic polarization curves were obtained in some solutions. The corrosion rates were greater in the order of Nb>Ta>Ti>Zr. Polarization curves showed that Ti, Ta and Zr passivated, however, Nb corroded. XRD patterns showed that Nb dissolved as niobate compounds. XPS spectra showed that Zr and Ti formed oxide films such as ZrO2 and TiO2 on their surface. SEM photographs indicated that uniform corrosion occurred for tested materials. There existed the differences of the stable species among the thermodynamic, corrosion test and surface analysis data. It is expected for expanding the thermodynamics data of these materials in the alkali region.
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  • Kimio Ito, Satoshi Wakai, Hirohito Tsurumaru, Takao Iino, Koji Mori, T ...
    2011 Volume 60 Issue 9 Pages 402-410
    Published: September 15, 2011
    Released: February 22, 2012
    JOURNALS FREE ACCESS
    Methane Producing Archaea (MPA), which could utilize metallic iron as an electron donor and CO2 as an electron acceptor and a carbon source, corroded an iron coupon severely in seawater medium under anaerobic condition (N2(80%)+CO2(20%)). Main component of corrosion products by MPA was FeCO3. MPA corroded the iron coupon more severely when they coexisted with SRB which could also utilize metallic iron as an electron donor. Corrosion rate of the iron coupon by MPA+SRB was about 2.3 times higher than that by MPA only under anaerobic condition (N2(80%)+CO2(20%)). Main component of corrosion products by MPA+SRB was FeCO3 like that by MPA.
    Corrosion rates of the iron coupon by MPA only, or MPA+SRB under anaerobic condition (N2(80%)+CO2(20%)) were higher than those under aerobic condition (Air) after the anaerobic corrosion experiments.
    Therefore, corrosive effects on iron by MPA+SRB, which can utilize metallic iron as an electron donor, should be considered as cause of microbiologically influenced corrosion in the anaerobic corrosive environments like oil fields, where CO2 and Cl are available.
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  • Mariko Nakamura, Hiroyuki Saito, Yasuhiro Higashi, Takashi Sawada, Tak ...
    2011 Volume 60 Issue 9 Pages 411-416
    Published: September 15, 2011
    Released: February 22, 2012
    JOURNALS FREE ACCESS
    Communication lines are usually composed of steel and other metallic components. For preventing corrosion of steel wire strands, Zn coating had been used. However, it became appear that some steel wire strands located in coastal areas still had been corroded. That was because air bone sea salt particles above the ocean are blown by the wind and adhere to the surface of metals. To protect steel wires against the atmospheric corrosion, Al coating was applied because of its higher corrosion resistance compared with that of Zn coating. This coating above still corroded which were at the coastal areas. Previous studies on this phenomenon showed that corrosion occurred in the interspace between the sealing tape which was used to inhibit the penetration of rain water and the wire strands. Since Japan is an island country and is surrounded by the sea, investigating the appropriate coatings for steel wire strands is important. We conducted the exposure test and compared three types of coated steel wire strands to investigate the effects of sacrificial anode on the corrosion in Miyake Island over 23 years.
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