Effect of liquid film thickness and flow velocity on the cathodic reaction of carbon steel under liquid film flow conditions

Otani, Kyohei; Igarashi, Takahiro

Journal of the Electrochemical Society, 172(9), p.091503_1 - 091503_8, 2025/09

https://doi.org/10.1149/1945-7111/ae02c8

Hydrogen absorption behavior of the R-SUS304ULC/Ta/Zr dissimilar metal joint under NaOH immersion

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi; Igarashi, Takahiro

Mechanical Engineering Journal (Internet), 12(4), p.24-00434_1 - 24-00434_7, 2025/08

https://doi.org/10.1299/mej.24-00434

In reprocessing plants of Japan, Zr and R-SUS304ULC piping are connected by a joint formed by explosive bonding with Ta sandwiched between R-SUS304ULC and Zr. The other hands, Ta corrodes with hydrogen evolution in NaOH solutions, which are used to decontaminate the equipment in reprocessing plants. This has led to concerns about hydrogen embrittlement of the joints via hydrogen absorption. However, there is a lack of studies on the hydrogen absorption behavior of such joints, and it is difficult to evaluate the amount of hydrogen absorbed by the joints under various decontamination conditions. In this study, immersion tests were conducted to the joint in NaOH solution to evaluate hydrogen absorption. Electrochemical measurements were conducted to examine the hydrogen absorption environment. The results showed that the amount of hydrogen absorbed into Ta in the joints decreased compared with that in pure Ta. The galvanic current measurements of Ta connected with R-SUS304ULC or Zr in NaOH solution indicated that the hydrogen evolution reaction was separated to the R-SUS304ULC and Zr surfaces and that the hydrogen absorption of Ta was suppressed.

Corrosion evaluation of steel surfaces using image processing

Igarashi, Takahiro

AI, Shimyureshon O Mochiita Rekka, Hakai Hyoka To Juyo Yosoku, p.323 - 329, 2025/05

Metal materials are used in various fields of daily life, especially in infrastructure like bridges, buried pipes, and concrete reinforcing bars. These materials are prone to corrosion, which can cause thinning, hydrogen generation, and embrittlement, leading to a loss of structural integrity and potentially serious accidents. Many studies have been conducted to address this issue. Recently, advances in computer performance have led to the development of corrosion diagnosis methods. One promising approach uses models that predict rust thickness and corrosion product composition by analyzing image data from surfaces, offering both ease of measurement and accuracy. This book introduces these methods, including color analysis, hyperspectral analysis, AI analysis, and feature point extraction.

Experimental and modeling study on ion concentration behavior in metal crevices in high-purity water

Soma, Yasutaka; Komatsu, Atsushi; Igarashi, Takahiro

Dai-71-Kai Zairyo To Kankyo Toronkai Koenshu (CD-ROM), p.253 - 256, 2024/11

In our previous study, we reported that Cl ions penetrating stainless steel crevices do not dissipate by diffusion, even in high-purity water (i.e., conductivity remains stable), likely due to electrochemical reactions inside and outside the crevice. This study further analyzes ion behavior by experimentally and computationally investigating ion concentration drivers in high-purity water. Results show that, at 50C, the crevice conductivity of SUS316L stainless steel reached 100 S/cm (100-1000 times bulk water). Modeling suggests this is due to metal cations and hydroxide ions from dissolved oxygen reduction. The dissolution rate was estimated at 10nA/cm.

Evaluation of corrosion on steel surface using image processing

Igarashi, Takahiro; Sugawara, Yu*; Otani, Kyohei; Aoyama, Takahito

Tetsu To Hagane, 110(15), p.1244 - 1250, 2024/11

https://doi.org/10.2355/tetsutohagane.TETSU-2024-058

Using two types of image processing techniques without machine learning, edge extraction processing and keypoint extraction processing, progressively corroded regions under rust layer from images of corroded steel surfaces was extracted. We found that there is a relatively good correlation between the keypoint strength obtained from the keypoint extraction processing for HSL transformed and histogram flattened corroded surface photographs and the corrosion depth after removing rust removal.

Estimation of the intergranular corrosion rate of stainless steel using cellular automata calculation considering stochastic process

Yamamoto, Masahiro*; Igarashi, Takahiro

Corrosion Modelling with Cellular Automata; European Federation of Corrosion Publications, Number 71, p.131 - 153, 2024/03

https://doi.org/10.1016/C2022-0-02639-8

In order to elucidate corrosion phenomena in spent fuel reprocessing plant, experimental corrosion tests and computer simulations were carried out. From experimental results, variation of intergranular corrosion rate were caused by following; (i) surface corrosion, (ii) increase of corrosion rate due to a part of grains dropping out, (iii) high corrosion rate due to continuous of dropping out of grains. Intergranular corrosion rates obtained from the simulation using the developed intergranular corrosion model were relatively good agreement with those from the experimental data.

Effect of dissolved Sr and Cs in HCl solutions on the corrosion potential of Type 316L stainless steel

Aoyama, Takahito; Sato, Tomonori; Ueno, Fumiyoshi; Kato, Chiaki; Sano, Naruto; Yamashita, Naoki; Igarashi, Takahiro

Zairyo To Kankyo, 72(11), p.284 - 288, 2023/11

https://doi.org/10.3323/jcorr.72.284

no abstracts in English

Evaluation of thermal diffusivity of uniaxial CFRP sheet by offset periodic laser heating method

Nagata, Sho*; Miyake, Shugo*; Igarashi, Takahiro; Ota, Hiromichi*; Nishi, Tsuyoshi*

Jikken Rikigaku, 22(2), p.105 - 111, 2022/06

Thermal easy axis and thermal diffusivity of uniaxial carbon fiber-reinforced plastic sheets were determined by a offset periodic laser heating method, and investigated relationship between the thermal easy axis and fiber orientation with different thickness of CFRP sheet specimen, experimentally. It was clarified that the orientation of the thermal easy axis spreads in the in-plane direction with the sheet thickness deceases. Then, thermal diffusivity of CFRP specimens in the out-of-plane and in-plane direction were measured by two method: a variable-frequency method and a variable-displacement method, respectively. In the results of the out-of-plane directions, thermal diffusivity almost consistent with the carbon fiber direction were obtained. In contrast, the in-plane directions of those were exhibited unexpected value. Moreover, thermal diffusivity determination by offset periodic heating method was carried out. Finally, it is found that the thermal diffusivity considering the thermal easy axis with fiber angle was different characteristics from the in-plane direction measurement.

Modeling and simulation of atmospheric corrosion of carbon steel considering environmental factor

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

Tetsu To Hagane, 107(12), p.998 - 1003, 2021/12

AA2020-0549.pdf:1.53MB

https://doi.org/10.2355/tetsutohagane.TETSU-2020-110

In order to clarify the effect of environmental factors on the amount of atmospheric corrosion of steel, novel model for predicting the reduction of atmospheric corrosion considering relative humidity and rain falls was developed. We conducted a one-year calculation simulation of atmospheric corrosion in Miyakojima City, Choshi City, and Tsukuba City using the developed model. Corrosion weight loss by the simulation could reproduce the measured value well. Corrosion weight loss at each point was greatly affected by the amount of flying sea salt, relative humidity, and rain falls.

Study on the thermal behavior of Carbon-Fiber-Reinforced-Plastic (CFRP) sheet using a periodic heating method

Nagata, Sho*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Igarashi, Takahiro; Miyake, Shugo*

Proceedings of 34th International Microprocesses and Nanotechnology Conference (MNC 2021) (CD-ROM), 2 Pages, 2021/10

Due to the increasing heat generation density of electronic devices, unidirectional Carbon-fiber-reinforced Plastic (CFRP) has gained interest as a heat-dissipating material owing to its high thermal conductivity, high anisotropy, and high strength. If CFRPs can be used to conduct heat in the desired direction of dissipation, more efficient thermal designs are possible. To control heat propagation, it is necessary to understand the heat propagation behavior within CFRPs at each fiber angle by determining the direction of heat propagation, referred to as thermal orientation. We previously demonstrated an approach for determining the thermal orientation of CFRPs using a periodic heating method, wherein the heat propagation in CFRPs was classified into two directions: the direction of the carbon fiber direction and the direction of the fiber-matrix interface. It has been suggested that the fiber-matrix interface has a significant effect on the heat propagation of CFRPs, which increases with the increase in CFRP thickness. However, the effect of CFRP thickness on thermal orientation is yet unknown. In the current study, we investigated the effect of the fiber-matrix interface on thermal orientation using the periodic heating method for CFRPs with varying thicknesses.