CORROSION ENGINEERING
Online ISSN : 1884-1155
Print ISSN : 0010-9355
Volume 30, Issue 8
Displaying 1-7 of 7 articles from this issue
  • Hydrogen Occlusion Behavior of Single Crystal of Iron and Mild Steel (Part 4)
    Koji Yamakawa, Takao Tsuruta, Shiro Yoshizawa
    1981 Volume 30 Issue 8 Pages 443-449
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    The hydrogen content, diffusion coefficient and permeation rate in single crystal of iron were measured with a modified electrochemical technique and were found to be in good agreement with Gonzalez' results. Screw dislocations introduced into a specimen resulted in the increased hydrogen content and decreased diffusion coefficient. From the theoretical analysis of interaction between the stress field of screw dislocation and hydrogen, the dislocation core was found to be a trapping site for hydrogen. The predicted temperature dependence of the content of such hydrogen agrees well with the experimental results.
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  • Kimio Sakai, Shujiro Morishita, Takashi Honda, Akira Minato, Masakiyo ...
    1981 Volume 30 Issue 8 Pages 450-455
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    The corrosion rate of carbon steel was measured in high purity water of specific conductivity less than 0.1μS/cm, at room temperature. Corrosion tests were performed at Japan Atomic Power Company, Tokai-2 Power Plant and in a loop at Hitachi Ltd., Hitachi Research Laboratory. The electrochemical measurements were done with a rotating disk electrode. The results indicated:
    1) The corrosion rate decreased with specific conductivity. For example, in aerated water of specific conductivity 0.06μS/cm, the corrosion rate was 1mg/dm2·mo. 2) The corrosion rate decreased with increasing dissolved oxygen concentration in the region 10ppb to 8ppm. 3) Effect of corrosion inhibition was maintained in water at velocity higher than 0.2cm/s. Thus, prevention of water stagnation may be beneficial in reducing the corrosion rate of carbon steel, and it is very beneficial for layup of plant to recirculate demineralized water through piping. 4) From the results of corrosion potential measurements, corrosion inhibition in high purity and high oxygen content water is due to the passivation of carbon steel.
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  • Rokuro Nishimura, Norio Sato
    1981 Volume 30 Issue 8 Pages 456-461
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    The composition, structure and thickness of passive films formed on iron by anodic oxidation in two steps with a preliminary oxidation at pH 11.50 followed by one hour oxidation in borate or phosphate solution at pH 8.42 have been investigated by the use of ellipsometric and electrochemical techniques, and the results are compared with those of passive films formed by a direct oxidation in the same solution. Chemical analyses of iron ion dissolved from the film and ellipsometric measurements of the film during galvanostatic catholic film reduction reveal that, irrespective of its formation procedure, the passive film is a two-layer film consisting of a deposit layer next to the solution and a barrier layer in contact with the metal. In borate solution, the compositions and the optical constants of the deposit and barrier layers exhibit almost no difference with different oxidation procedures, except for a minor difference in the barrier layer formed at less noble potential. In phosphate solution, the deposit layer composition is scarcely affected by oxidation procedure, but the barrier layer composition differs in different oxidation procedures with an Fe(II) ion-rich oxide in direct oxidation and a magnetite-like oxide in two step oxidation. The optical constants of the deposit and barrier layers and the ion enrichment at the deposit/barrier interface are found to depend on the oxidation procedure. The thickness of the deposit layer formed by direct oxidation is always thicker than that of the deposit layer formed by two step oxidation, but the barrier layer thickness is determined solely by the overpotential applied regardless of the oxidation procedure. The results are explained in terms of the ion selective property of the film, which differs in different oxidation procedures.
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  • Toshiaki Kodama, Tetsuo Fujii, Haruo Baba
    1981 Volume 30 Issue 8 Pages 462-468
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    Corrosion tests of three types of water supply pipes (carbon steel, galvanized steel, and copper) were carried out at seven water works of major cities in Japan (Tokyo, Osaka and Nagoya). In the test, the treated water of the works was allowed to flow through pipes in a once-through testing apparatus. The results obtained are summarized as follows: 1) Water temperature alone influences the corrosion rate of carbon steel. 2) The corrosion rate of galvanized layer is proportional to the activity of H+(10-pH). This trend is highly pronounced in low-pH water with high acidity (dissolved CO2). 3) Corrosion trend of copper is similar to that of galvanized steel; corrosion rate increases with decreasing pH and increasing acidity. 4) Corrosion potential of galvanized steel shifted towards nobler values with time, while steel and copper showed relatively constant values. The reciprocal of polarization resistance showed fairly good correlation for galvanized steel with corrosion rate measured by weight loss, when iR-drop compensation was properly made.
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  • Shigenori Yamauchi, Shiro Sato
    1981 Volume 30 Issue 8 Pages 469-477
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    This paper reviews the corrosion problems of copper tube experienced in fresh water service. Following three distinct types of corrosion are discussed; (1) dissolution of copper, (2) pitting corrosion, and (3) erosion corrosion.
    Dissolved copper ion, which may cause green stains by forming insoluble cupric soap or accelerate the corrosion of other metals, is associated with the cupro-solvency of water. Decrease of pH and/or increase of carbon dioxide raise the dissolution rate of copper.
    Pitting corrosion of copper tubes is generally classified in two types, i. e., Type I pitting experienced mainly in cold water in Europe and USA, and Type II pitting experienced mainly in hot water in Japan, Sweden and Germany. Type I is attributed to carbon film on the tube surface and/or to water quality. Carbon film can raise the potential of copper tube higher than the critical pitting potential, 100 to 170mV vs. SCE. Type II pitting is associated with chemical composition of water, i. e., pH and the ratio of HCO3-/SO42-. Excess of chlorination also plays an important role, which can raise the potential of copper tube higher than the critical pitting potential, 150mV vs. SCE, to cause Type II pitting corrosion.
    As regards the erosion corrosion of copper tubes, importance of two factors must be stressed; one is fluid dynamic conditions which affect mechanical breakdown of the protective film on the tube surface, and the other is chemical composition of water which affects the stability of the film formed on the tube surface.
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  • Yoshiharu MATSUDA
    1981 Volume 30 Issue 8 Pages 480
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
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  • Takehiko KAKEHI
    1981 Volume 30 Issue 8 Pages 482-483
    Published: August 15, 1981
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
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