Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Volume 64 , Issue 9
Showing 1-6 articles out of 6 articles from the selected issue
  • Kunitsugu Aramaki
    2015 Volume 64 Issue 9 Pages 401
    Published: September 15, 2015
    Released: March 03, 2016
    Recently, passive film breakdown of Fe has been investigated in solutions of various anions by measuring the time required for breakdown, tbd and permeation of anions into the passive film using X-ray photoelectron spectroscopy. The results have been discussed on the basis of the hard and soft acids and bases (HSAB) principle. In previous study, the pitting and repassivation potentials of a passivated Fe electrode were measured in a borate buffer solution containing Cl. The effects of added I on pit initiation and growth were discussed using electronprobe microanalysis and based on the HSAB principle. In this paper, the results of the previous investigation are interpreted by considerations of the recent work in more detail.
    Download PDF (1743K)
Research Paper
  • Toru Yoshimura, Kyoji Niitani, Michikazu Tawara, Taichirou Nagi
    2015 Volume 64 Issue 9 Pages 405-413
    Published: September 15, 2015
    Released: March 03, 2016
    Reduction of the chloride ion ingress in concrete will be greatly improved by adding blast furnace slag fine powder to concrete. Its durability has, however, not been fully verified in actual corrosive environment. In addition, the possibility of reinforcing steels' corrosion has remained as ever; hence a technique for observing and predicting the internal corrosive environment needs to be established. In this study, exposure testing has been operated at a site near seashore to verify the durability of concrete mixed with ground granulated blast-furnace slag 6000. In the test, the apparent diffusion coefficient has been investigated and electrical potential of rebar in concrete has been telemetered with a monitoring system newly developed in this study. Main conclusions obtained in this study are as follows: [I] the apparent diffusion coefficients obtained from the specimens exposed for three years show the curve close to the prediction equation defined in the Standard Specification for Concrete Structures with changing the third term of the equation. [II] The monitoring system has allowed to observe corrosion potential in a long period and to monitor remotely the changes of corrosive environment over time.
    Download PDF (3678K)
  • So Aoki, Tomomi Taniguchi, Jun'ichi Sakai
    2015 Volume 64 Issue 9 Pages 414-420
    Published: September 15, 2015
    Released: March 03, 2016
    The objective of this study is to clarify the preferential dissolution mechanism of a duplex stainless steel (DSS) at its corrosion potential (about -0.15 V vs.SHE) by means of Scanning Electrochemical Microscope (SECM) observation of the corrosion reactions on the ferritic phase (α phase) and the austenitic phase (γ phase) of a DSS, respectively. Probe electrode was fixed above α and γ each phase of DSS at corrosion potential in 1 mol/l HCl aqueous solution. Potential of the probe electrode was polarized toward noble direction, from -0.10 V to 1.4 V (SHE), at a potential scan rate of 20 mV/s, and probe current was measured. In a probe potential range of 0~0.70 V (SHE), anodic current due to hydrogen oxidation reaction could be detected. This anodic current was larger above γ phase than that above α phase. In a probe potential range of 0.70~1.2 V (SHE), anodic current due to Fe2+ oxidation reaction to Fe3+ could be detected. This anodic current was larger above α phase than that above γ phase. On the α phase, the anodic dissolution reaction occurred preferentially at the DSS corrosion potential, while on the γ phase, the cathodic reduction reaction of hydrogen ion occurred preferentially.
    Download PDF (2403K)