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Journal Articles

Synergistic effect of aluminum lactate and sodium molybdate on freshwater corrosion of carbon steel under irradiation

Otani, Kyohei; Kato, Chiaki; Igarashi, Takahiro

Corrosion, 79(11), p.1277 - 1286, 2023/11

Journal Articles

Approach to elucidate corrosion mechanism on metal surface using first-principles calculations

Igarashi, Takahiro; Otani, Kyohei; Komatsu, Atsushi; Kato, Chiaki; Sakairi, Masatoshi*

Bosei Kanri, 66(4), p.141 - 145, 2022/04

Metal corrosion is a material deterioration phenomenon based on electrochemical reactions on an atomic scale. In this paper, various methods for acquiring physical properties on metal surfaces using first-principles calculations were described. As examples of applying first-principles calculation to metal corrosion, the effect of hydrogen adsorption on the metal surface on the potential change and the effect of cation atoms in the aqueous solution on the corrosion resistance of the metal were reported.

Journal Articles

Effect of oxygen concentration on corrosion rate of carbon steel in air/solution alternating condition

Otani, Kyohei; Ueno, Fumiyoshi; Kato, Chiaki

Zairyo To Kankyo, 71(2), p.40 - 45, 2022/02

The purpose of this study is to investigate the effect of oxygen concentration in the air on the corrosion rate of carbon steel in an air/solution alternating environment in the low oxygen concentration range and to clarify the corrosion rate and corrosion mechanism of carbon steel depending on the oxygen concentration in air by the mass change of specimens before and after the corrosion test and observing the iron rust layer formed on the surface of carbon steel. The corrosion rate increases with increasing oxygen concentration in the air, and the gradient of the corrosion rate decreases gradually. The maximum erosion depth increased with increasing oxygen concentration except for the case of 1% oxygen concentration, however, the maximum erosion depth for 1% oxygen concentration was larger than that for 5% air oxygen concentration.

Journal Articles

Corrosion of carbon steel in the simulated air/solution interface environment

Otani, Kyohei; Kato, Chiaki

Zairyo To Kankyo, 70(12), p.480 - 486, 2021/12

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 ($$gamma$$-FeOOH), rust crust layer (Fe$$_{3}$$O$$_{4}$$), inner crystal (Fe$$_{3}$$O$$_{4}$$), 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.

Journal Articles

Hydrogen absorption mechanism into iron in aqueous solution including metal cations by laser ablation tests and first-principles calculations

Igarashi, Takahiro; Otani, Kyohei; Kato, Chiaki; Sakairi, Masatoshi*; Togashi, Yusuke*; Baba, Kazuhiko*; Takagi, Shusaku*

ISIJ International, 61(4), p.1085 - 1090, 2021/04

 Times Cited Count:0 Percentile:8.46(Metallurgy & Metallurgical Engineering)

In order to clarify the effect of metal cations (Zn$$^{2+}$$, Mg$$^{2+}$$, Na$$^{+}$$) in aqueous solution on hydrogen permeation into iron, the amount of hydrogen permeation from iron surface was measured by electrochemical tests with a laser ablation. Moreover, in order to obtain the basic mechanism of hydrogen permeation with metal cation, first-principles calculations were used to acquire the adsorption potential of the metal cation and the electronic state around iron surface. By Zn$$^{2+}$$ in solution, anodic reaction on ablated surface by laser irradiation was suppressed. Also, by quantum analysis Zn atoms were chemically bonded stronger than Na and Mg atoms to iron surface. It was suggested that the dissolution reaction of iron was suppressed by the formation of the Zn layer, and that lead suppression of hydrogen permeation into iron.

Journal Articles

Effect of seawater components on corrosion rate of steel in air/solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Kato, Chiaki

Zairyo To Kankyo, 69(9), p.246 - 252, 2020/09

The purpose of this study was to investigate the effect of artificial sea water concentration on the corrosion rate of carbon steel under air/solution alternating condition, and to clarify the corrosion mechanism of carbon steel that changes with artificial seawater concentration. Mass measurements showed that the corrosion rate of carbon steel in the alternating condition accelerates with increasing concentration in the concentration region between deionized water to 200 times diluted artificial seawater (ASW), and the corrosion rate decreases with increasing concentration in the concentration region between 20 times diluted ASW to undiluted ASW. It can be considered that the reason why the carbon steel corrosion was suppressed in highly concentrated artificial seawater would Mg ions and Ca ions in the artificial seawater precipitate and cover on the surface due to the increase in pH near the surface by oxygen reduction reaction.

JAEA Reports

Spatial uniformity of negative ion beam in magnetically filtered hydrogen negative ion source; Effect of the H$$^{-}$$ ion production and transport processes on the H$$^{-}$$ ion beam intensity profile in the Cs-seeded negative ion source (Joint research)

Takato, Naoyuki; Tobari, Hiroyuki; Inoue, Takashi; Hanada, Masaya; Seki, Takayoshi*; Kato, Kyohei*; Hatayama, Akiyoshi*; Sakamoto, Keishi

JAEA-Research 2008-031, 44 Pages, 2008/03

JAEA-Research-2008-031.pdf:4.05MB

The origin of the H$$^{-}$$ ion beam non-uniformity under the Cesium seeded condition was studied in the JAEA 10 Ampere negative ion source by measuring the profiles of the beam intensity and plasma parameters. The numerical analyses, such as the trace of particles (the electron, the H$$^{0}$$ atom and the H$$^{-}$$ ion) trajectories using the Monte Carlo method, were also applied to consider the experimental results.

Journal Articles

Numerical analysis of primary electrons in a tandem-type negative ion source

Kato, Kyohei*; Takado, Naoyuki*; Hatayama, Akiyoshi*; Hanada, Masaya; Seki, Takayoshi; Inoue, Takashi

Review of Scientific Instruments, 77(3), p.03A535_1 - 03A535_3, 2006/03

 Times Cited Count:12 Percentile:52.35(Instruments & Instrumentation)

To clarify physics mechanism of plasma spatial nonuniformity observed in tandem-type negative-ion sources, primary electron-transport process has been analyzed by a three-dimensional Monte Carlo simulation code. In the model, equations of motion for electrons are numerically solved. Geometry and magnetic-field configuration of the JAEA 10 Ampere negative ion source are taken into account. Various collision processes with neutral particles are also included in the model. The simulation results show that (1) the primary electrons have been lost from the source region to the extraction region due to magnetic drift in the magnetic filter, and then (2) there is another magnetic drift near the sidewalls, where a sum of magnetic field of the filter and the cusp field for plasma confinement allows electron drift towards the extraction region. A sequence of these magnetic drifts would increase the electron temperature in local area of extraction region, which resulted in loss of negative ions.

Journal Articles

Numerical analysis of the spatial nonuniformity in a Cs-seeded H$$^{-}$$ ion source

Takado, Naoyuki*; Hanatani, Junji*; Mizuno, Takatoshi*; Kato, Kyohei*; Hatayama, Akiyoshi*; Hanada, Masaya; Seki, Takayoshi; Inoue, Takashi

Review of Scientific Instruments, 77(3), p.03A533_1 - 03A533_3, 2006/03

 Times Cited Count:14 Percentile:56.72(Instruments & Instrumentation)

Surface production and transport process of H$$^{-}$$ ions are numerically simulated to clarify the origin of H$$^{-}$$ beam non-uniformity. A three-dimensional transport code using Monte Carlo method has been applied to productions of H$$^{0}$$ atoms and H$$^{-}$$ ions in a large negative ion source under the Cs seeded condition. The results show that a large fraction of hydrogen atoms are produced in a high electron temperature region. This leads to a spatial non-uniformity of H$$^{0}$$ atom flux to the plasma grid where H$$^{0}$$ atoms capture electrons and converted to H$$^{-}$$ ions. In addition, most surface-produced H$$^{-}$$ ions are extracted even through the high electron temperature region without destruction.

Oral presentation

Numerical analysis of the production profile for hydrogen atoms and negative ions in a Cs-seeded large negative ion source

Takato, Naoyuki; Hanatani, Junji*; Kato, Kyohei*; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Tobari, Hiroyuki; Hanada, Masaya; Inoue, Takashi; Taniguchi, Masaki; Hasebe, Mieko; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on metal corrosion using computer simulation method

Igarashi, Takahiro; Otani, Kyohei; Komatsu, Atsushi; Irisawa, Eriko; Ueno, Fumiyoshi; Yamamoto, Masahiro; Kato, Chiaki

no journal, , 

Metal corrosion leads various problems such as degradation of structural materials. Since metal are used in various places ranging from large-scale structures such as nuclear power plants, chemical plants and bridges, to small facilities such as water pipes, many studies have been conducted to elucidate the basic mechanism of metal corrosion. In recent years, corrosion research using computational analysis has often conducted by high performance computing. In this presentation, we introduce our research on prediction of surface morphology by intergranular corrosion using macroscopic computational model, and surface adsorption reaction of chemical species in solution by quantum calculation.

Oral presentation

Effect of concentration of artificial sea water on corrosion behavior of steel in air-solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Kato, Chiaki

no journal, , 

Corrosion tests of carbon steel was carried out in air-solution alternating condition in previous study. It has been reported that the corrosion rate of carbon steel exposed in air-solution alternating condition was accelerated compare with the steel exposed in solution. In this study, it was investigated that the effect of concentration of model sea water on corrosion rate of carbon steel in air-solution alternating condition. The mass measurement in corrosion tests clarified that the corrosion rate of carbon steel in the 200 times diluted model sea water is fastest during various model sea water. Cross-sectional analysis of iron rust layer formed on carbon steel after corrosion tests indicated that the corrosion rate of carbon steel in model sea water is decreased by precipitation of metal cations containing in model sea water.

Oral presentation

Effect of oxygen concentration on the corrosion rate of carbon steel under air/solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Kato, Chiaki

no journal, , 

It was reported that the corrosion rate of carbon steel was accelerated under the air/solution alternating condition. In this presentation, it is investigated that the effect of oxygen concentration on the corrosion rate of steel under the air/solution alternating condition. As a result, the corrosion rate of carbon steel under the air/solution alternating condition did not increase linearly with increasing oxygen concentration in the air, and the slope in the low concentration range (0-5%) is greater than in the high concentration range (5-20.8%). This suggests that the corrosion rate may be accelerated around the air/solution interface on the inner surface of the PCV if even a small amount of oxygen is introduced into the PCV during the debris removal process.

Oral presentation

Effect of cations in solution on hydrogen absorption behavior; Theoretical discussion from quantum mechanics

Igarashi, Takahiro; Otani, Kyohei; Komatsu, Atsushi; Kato, Chiaki

no journal, , 

We discussed the effect of cations in solution on hydrogen absorption into iron using First-principles calculation with solution approximation. It was confirmed that the Zn ions in solution have a strong chemical bond with the Fe atoms on surface. This leads that the formation of a metal film by Zn adsorption may have inhibited the Fe dissolution reaction and suppressed hydrogen absorption.

Oral presentation

Synergistic effect of aluminum lactate and sodium molybdate on freshwater corrosion inhibition of carbon steel

Otani, Kyohei; Ueno, Fumiyoshi; Kato, Chiaki

no journal, , 

In order to develop a novel corrosion inhibitor that is suitable for the 1F environment, it was focused on aluminum lactate, which had not been focused on as a corrosion inhibitor. It was found that aluminum lactate had a synergistic effect and high corrosion inhibition ability when mixed with sodium molybdate. As a result of surface XPS analysis, it was found that the corrosion of carbon steel was inhibited by the formation of aluminum and molybdenum oxide films on the carbon steel surface.

Oral presentation

Corrosion discrimination method from surface images

Igarashi, Takahiro; Otani, Kyohei; Aoyama, Takahito; Kato, Chiaki

no journal, , 

It is one of the important issues to understand the corrosion condition inside the material nondestructively in the integrity assessment of large structures such as bridges and plants. In this presentation, we attempted to determine the corrosion state from the surface image before rust removal by using the contour extraction method based on the discontinuity of luminance in the neighboring pixels of the image and the feature point extraction method using the gradient of the corner and luminance of the neighboring pixels. As a result, it was found that the Adaptive Gaussian and Canny methods could be used for contour extraction, and the Agast Feature Detector method could be used for feature point extraction to predict the vicinity of corrosion points.

Oral presentation

Corrosion mechanisms of carbon steel in the simulated air/solution interface

Otani, Kyohei; Kato, Chiaki

no journal, , 

Cooling water is circulated and injected into the containment vessel (PCV) of Fukushima Daiichi Nuclear Power Station (1F) Units 1-3, and nitrogen gas is injected and filled to prevent hydrogen explosion and to control corrosion of steel materials. In order to maintain the integrity of the PCV facilities over a long period of time until the decommissioning of the reactors, it is necessary to predict the corrosion behavior of carbon steel, which is the main structural material, and in particular to study the factors that may accelerate corrosion. From the internal investigation of the PCV, it was confirmed that carbon steel, which is the material inside the PCV, is exposed to an environment in which the gas and liquid environments alternate near the air/solution interface (Air/solution alternating environment). It has been reported that metallic materials are covered with a thin liquid film near the air/solution interface, and that the corrosion rate of steel is accelerated when there is a thin water film on the steel surface compared to that in solutions. In this presentation, the corrosion test of carbon steel was conducted using a rotating corrosion test apparatus to simulate the air/solution alternating environment inside the 1F PCV, and the corrosion rate and corrosion mechanism of carbon steel obtained from the results of mass measurement, observation and analysis will be presented.

Oral presentation

Corrosion behavior of carbon steel under micrometer-order controlled flowing liquid film

Otani, Kyohei; Kato, Chiaki; Ueno, Fumiyoshi

no journal, , 

The effects of flowing liquid film thickness and flow rate on the corrosion behavior of carbon steel under flowing liquid film were clarified by using a novel corrosion equipment.

Oral presentation

Effects of water radiolysis on the corrosive environments of overpack at the transition period

Sato, Tomonori; Hata, Kuniki; Igarashi, Takahiro; Otani, Kyohei; Kato, Chiaki

no journal, , 

It is estimated that the outer surface of the overpack of high-level radioactive waste during the transition period of the geological disposal is exposed to the groundwater percolated into the bentonite under irradiation. So, evaluations of water radiolysis considering the contribution of bentonite is one of the important factors to understand the corrosive environment. In this study, the results of the contribution of impurities leaching from bentonite and coexistence of bentonite in the water radiolysis are reported.

Patent

水系における防食剤および防食方法

大谷 恭平; 加藤 千明

not registered

JP, 2021-043875  Patent licensing information  Patent publication (In Japanese)

【課題】本発明は、添加コストや排水の水処理コストが低い防食剤および防食方法を提供することを課題とする。 【解決手段】本発明は、(A)乳酸アルミニウム、および(B)無機酸塩および有機酸塩から選ばれる1種または2種類以上を含有する、水系における金属部材の防食剤、および同防食剤を用いた水系における金属部材の防食方法を提供する。

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