Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Volume 67 , Issue 4
Showing 1-8 articles out of 8 articles from the selected issue
Conference Publication
  • Hanami Tezuka, Shogo Tsukazawa, Hitoshi Yashiro, Hidenori Inabe, Yoich ...
    2018 Volume 67 Issue 4 Pages 164-167
    Published: April 15, 2018
    Released: September 27, 2018

    In absorption refrigeration systems, molybdate is used as a key inhibitor against corrosion of steel, although it is liable to precipitate because of its limited solubility in a concentrated LiBr solution. In this research, the use of sulfite is proposed as a precipitation inhibitor for molybdate and its effect on the passivation of iron is examined. The effect of the stronger passivator of nitrate on the actions of sulfite is also investigated. The results show that sulfite decreases the amount of corrosion of iron and promotes the formation of the oxide layer (MoO2, Fe3O4) on the surface of iron irrespective of presence of nitrate. Thus, sulfite is concluded as an effective additive in an absorption refrigerator for better control of molybdate concentration and corrosion of iron.

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  • Masahiro Sakai, Masato Kumagai, Akira Osaka, Tomoyoshi Irie, Hiroshi Y ...
    2018 Volume 67 Issue 4 Pages 168-171
    Published: April 15, 2018
    Released: September 27, 2018

    C-ring stress corrosion tests under three conditions were carried out to investigate the effect of humidity and oxygen concentration on stress corrosion cracking of phosphorous deoxidized copper tubes. Three conditions were high humidity, low humidity and low oxygen conditions. The relative humidity and oxygen concentration were 100% and about 20% respectively in the high humidity condition. The air in the container with desiccant agent stored at a relative humidity of 90 to 95% in the low humidity condition. In the low oxygen condition, the air in the container was replaced by the nitrogen gas and kept the concentration of oxygen less than 5% during the exposure test. Although stress corrosion cracks occurred in the specimens exposed under both high humidity and low oxygen conditions, the time to occurrence of SCC under the low oxygen condition was longer than that under the high humidity condition. No SCC and intergranular corrosion developed in the specimen exposed under the low humidity condition for one week. It was found that lowering the humidity has an inhibitive effect on the SCC of the phosphorous deoxidized copper tube.

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  • Gaku Kitahara, Aya Tsuji, Takashi Asada, Tomohiro Suzuki, Keitaro Hori ...
    2018 Volume 67 Issue 4 Pages 172-178
    Published: April 15, 2018
    Released: September 27, 2018

    Corrosion rate and diffusible hydrogen content of high tensile steel under constant load testing (CLT) in pH2 corrosive solution were investigated using electrochemical impedance spectroscopy (EIS) and thermal desorption spectroscopy (TDS). Rp-1 which is an index of corrosion rate increased as stress increased, which was correlated with the result of corrosion weight loss. This considered to be due to an increase in active nascent surfaces with increasing stress. Diffusible hydrogen content increased with stress, in particular by plastic deformation. The latter was more affected by the effect of corrosion rate and diffusible hydrogen content on stress. In other words, we have concluded that diffusible hydrogen content which related to hydrogen embrittlement was more affected by defects in steels by deformation than hydrogen entry from surface corrosion reaction in corrosion environment.

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Research Paper
  • Matsuho Miyasaka
    2018 Volume 67 Issue 4 Pages 179-184
    Published: April 15, 2018
    Released: September 27, 2018

    An example of Al corrosion in organic solvent is shown here. Severe Al corrosion occurred in a short time in Polypropylene Glycol Monobutyl Ether (PGME) including about 2% of N-Phenyl-1-Naphtylamine at a temperature of 110℃. An investigation showed that the corrosive medium of Al was PGME itself, the principal component of the solvent. Al is replaced with H of OH group, a component of PGME, to form an organic Al compound, dissolving in PGME, while H separated from PGME changed into hydrogen gas. Here we show the corrosion status, the procedure and results of the investigation, and the results of the corrosion reproduction test.

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