CORROSION ENGINEERING
Online ISSN : 1884-1155
Print ISSN : 0010-9355
Volume 37, Issue 10
Displaying 1-7 of 7 articles from this issue
  • Atsushi Chiba, Tadahiko Ogawa
    1988 Volume 37 Issue 10 Pages 595-600
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    The effect of direction of the magnetic force on dissolution of copper, zinc and brass (Cu/Zn=6/4) were examined. Their sample plates were dissolved in a 5cm3 nitric acid solution and their dissolution rates were determined. Corrosion potential and corrosion current density also were determined by use of polarization curves. The specimens were examined by using an X-ray diffractometer to determine the crystal plane of prefered dissolution which were expressed in terms of the texture coefficient. On copper and brass, inhibition effects were enhanced with increasing magnetic flux densities. Inhibition was considered to be due to the formation of oxidation film. The relation between dissolution rate and angles of line of magnetic force was obtained as follows: U1=U0/sin|(90°-θ)|, (θ=0-45°, 135°-225°, 315°-360°) and U1=U0cos|(θ-90°)|, (θ=45°-135°, 225°-315°), where θ was angle of line of magnetic force, U0 was dissolution rate at θ=90° and U1 was dissolution rate at other angles. It was considered that dissolution rate was not related to angle of the line of magnetic force, but was related to magnetic flux densities on a vertical component of metal surface. Corrosion potential shifted negative and corrosion current densities decreased with increase in magnetic force. Corrosion of the planes of metal surface was also affected. On zinc, corrosion rate, corrosion potential and corrosion current density hardly underwent the effect of magnetic field. It seemed that the solution was starred due to generation of hydrogen gas.
    Download PDF (706K)
  • Hideo Kanamori, Mituaki Iino, Shigeo Tsujikawa
    1988 Volume 37 Issue 10 Pages 601-607
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    Cast iron and carbon steel become passive in caustic hydraulic luburicants of aqueous glycol solution with help of slightly dissolved oxygen from the air. They have performed well over 10 years in practical uses, but have some service experiences of crevice corrosion in the environments, as observed for stainless steels in neutral solutions. In this report causes of crevice corrosion are examined in terms of pH and critical potentials. pH values of A-B measured for solutions in practical cases of crevice corrosion were higher than depassivation pH (pHd), which shows that the pH values are not responsible to the corrosion. Spontaneous electrode potential (ESP) for the steels passivated in the solution was determined to be about -0.15V vs. SCE. Critical potentials, VCREV, above which crevice corrosion initiates and continues to grow over 20μm in depth were measured as a function of Cl- content of the solution and found to coincide to repassivation potential, ER*, CREV for crevice corrosion shallower than 20μm. Cl- more than 10ppm makes VCREV or ER*, CREV less noble than ESP and might lead to the crevice corrosion in the cases studied. To control Cl- content blow 10ppm is an effective way to avoid the crevice corrosion.
    Download PDF (1598K)
  • Toshinori Ozaki, Ichiro Gyobu, Yuichi Ishikawa
    1988 Volume 37 Issue 10 Pages 608-613
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    Several case histories of corrosion failure of turbo compressor impellers are presented and the corrosion conditions, materials experiences, a principal cause of the impeller failure and possible ways to prevent the failure are discussed. The corrosion conditions in the turbo compressor are varied from mild to severe depending on combination of the operating atmosphere and the selection of materials for construction. The deposition of basic copper sulphate, antlerite formed by the reaction of SO2 contaminated air and the copper alloy heat exchanger tube, on the impeller surface results in a strongly oxidative and acidic corrosion environment for the impeller. Then a low alloyed high strength steel impeller suffers severe corrosion attack, while 13Cr martensitic stainless steel is subjected to stress corrosion cracking via active path corrosion. Possible ways to prevent the corrosion failure are change of the heat exchanger tube material and introduction of a mist separator to reduce and avoid the formation of antlerite. Further, full desensitization of stainless steel impeller and the use of 17-4PH stainless steel are very effective.
    Download PDF (1509K)
  • Hidemasa Nonaka, Shigemitsu Okada, Koji Yamakawa, Harushige Tsubakino, ...
    1988 Volume 37 Issue 10 Pages 614-617
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    The mechanical properties of steel buried in marine clay at various cathodic potentials in the range from -0.85 to -3.0V vs. Cu/CuSO4 were studied by means of slow strain rate test. The content of hydrogen in the steel entered from over protection environment was also measured by an electrochemical method (Ni-plating method). The reduction in area decreased drastically at -2.0V and downed to one-half of the value obtained in the air at less noble potential than -2.5V. The hydrogen content in the steel increased almost exponentially with cathodic potential. The fractured surface at -3.0V revealed typical quasi-cleavage mode. Then, the decrease in the reduction in area would be due to the influence of hydrogen which entered from steel surface under over protection.
    Download PDF (1085K)
  • Yoshio Harada
    1988 Volume 37 Issue 10 Pages 618-625
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    Metallic coatings are widely used in practice as an effective meams for the corrosion control of metallic materials. For the iron and steel structures used in natural environments such as the air atmosphere, fresh water, sea water and soil, zinc and aluminium coatings are applied. These metallizations are carried out by hot dipping and thermal spraying. On the other hand, for the high temperature oxidation and/or corrosion environments are frequently applied the simple chromium or aluminium or the alloy coating with these metals by means of hot dipping, diffusion coatings, thermal spraying and physical vapor deposition. This paper described about the different metallic coating methods, characteristics of coatings, their mechanisms for corrosion protection and applications.
    Download PDF (2437K)
  • Hidetsugu Sasaki
    1988 Volume 37 Issue 10 Pages 626-632
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    The cost of corrosion is estimated to be a few percent of the Gross National Product, and considerable extent of which could be saved by using existing technology. Corrosion database systems help utilizing exisiting data and thus contribute to the realization of these cost savings. Forefront of factual databases and expert systems was reviewed. It is expected that better factual databases and good algorithmes must be complied. Knowledge based systems integrated with other application software are very promising.
    Download PDF (1056K)
  • [in Japanese], Toshio Shibata
    1988 Volume 37 Issue 10 Pages 639-641
    Published: October 15, 1988
    Released on J-STAGE: October 30, 2009
    JOURNAL FREE ACCESS
    Download PDF (522K)
feedback
Top