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Soma, Yasutaka; Kato, Chiaki
Zairyo To Kankyo 2022 Koenshu (CD-ROM), p.219 - 220, 2022/05
It is important to understand the electrochemical properties of stainless steel in environment created within crevice of stainless steel in high temperature water (crevice environment). This is because acidification and concentration of impurity ions occur in the crevice environment and this is common inside the stress corrosion crack. In this study, we reproduced the crevice environment in bulk scale and investigated mainly the effect of Cr concentration on the electrochemical properties of Fe-Cr-Ni alloys. Polarization curves of Fe-20Ni-xCr (x=16.4, 23, 26) were measured in water with a temperature of 288
C, a Cl concentration of 2
10
mol/dm
, a pH value of about 4.5, and a dissolved hydrogen concentration of 10 ppb. The peak currents of active dissolution (at -400 mV) and passive current density (at -50 mV) for specimens with Cr concentrations x = 16.4, 23, and 26% were approximately 13.8, 15.9, 10.0 
Acm
, and 18.4, 8.5, 8.5 Acm, respectively. Although the current values of x=26 were slightly lower in both cases, it was concluded that there was no clear dependence of the polarization curve on Cr concentration in this environment.
alternating immersion environmentIshijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi
no journal, ,
In order to investigate the corrosion behavior of SUS304ULC/Ta/Zr dissimilar metal joint used in nuclear fuel reprocessing plants during decontamination, alternate immersion tests with 1 to 7 mol/L NaOH and HNO were carried out for dissimilar metal joint and pure Ta. From immersion test results, surface observations, and test solutions analysis after immersion test, it was considered that the joints were corroded by Ta during immersion in sodium hydroxide. The corrosion rate of Ta in dissimilar metal joint was found to be lower than that of pure Ta in some immersion conditions. It is considered that the corrosion of Ta in such an environment was inhibited by the fact that the corrosion potential of Ta was nobler than that of pure Ta due to contact with SUS304ULC.
Otani, Kyohei
no journal, ,
This is a comprehensive paper of the corrosion of carbon steel in air/solution alternating condition. From cross-sectional observation and analysis of the iron rust layer formed on the surface of carbon steel in the alternating condition, it was found that a multilayered iron rust layer composed of red rust layer, rust crust layer, inner crystal, and inner rust layer was formed on carbon steel. The multi-layered iron rust layer would accelerate the cathodic oxygen reduction reaction, and the reason why the corrosion rate of the carbon steel in the alternating condition was accelerated. The effect of artificial seawater (ASW) composition on the corrosion rate of carbon steel in air/solution alternating condition was investigated. It was found that the corrosion rate increased with increasing concentration from pure water to 200 times diluted ASW, and decreased with increasing concentration from 20 times diluted ASW to no diluted ASW. The Mg and Ca ions in ASW precipitated on the reaction interface and formed a metal cation layer, which inhibited the oxygen reduction reaction, and thus the corrosion of carbon steel was inhibited in the highly concentrated ASW. This is a commemorative lecture for the awarding of the Progress Award by the Japan Society of Corrosion Engineering.