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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.

Journal Articles

Auger electron spectroscopic analysis of corrosion products formed on A3003 aluminum alloy in model fresh water with different Zn$$^{2+}$$ concentration

Otani, Kyohei; Islam, M. S.*; Sakairi, Masatoshi*; Kaneko, Akira*

Surface and Interface Analysis, 51(12), p.1207 - 1213, 2019/12

 Times Cited Count:0 Percentile:100(Chemistry, Physical)

The corrosion morphology and composition of corrosion products of A3003 formed in model fresh water with different Zn$$^{2+}$$ concentrations were investigated by immersion tests combined with surface observations and analysis using an auger electron spectroscope (AES). The cross-sectional AES observations showed that the thickness of the corrosion product layer formed on A3003 decreases with increases in the Zn$$^{2+}$$ concentration of the model fresh water. A cross-sectional AES point analysis suggested that the corrosion products formed on the A3003 in the Zn$$^{2+}$$ containing model fresh water (Zn$$^{2+}$$ $$>$$ 0.1 mM) have a multi-layer structure, and that the inner of Zn-rich layer would have high corrosion protective properties.

Journal Articles

Analysis for the mechanism of accelerated corrosion on low alloy steel in air-solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi

Zairyo To Kankyo, 68(8), p.205 - 211, 2019/08

In the present study, the iron rust layer formed on the low ally steel in air-solution alternating condition was investigated by cross-sectional observation and analysis, and the mechanism of accelerated corrosion of the steel in the alternating condition was clarified. Observation and analysis showed that the multi-layered iron rust layer composed of red rust layer (FeOOH), rust crust layer (Fe$$_{3}$$O$$_{4}$$), inner crystal (Fe$$_{3}$$O$$_{4}$$), and inner rust layer was formed on the low alloy steel. It can be considered that the multi-layered iron rust layer accelerated the cathodic reaction rate of the steel in the alternating condition. This acceleration would be the reason why the corrosion rate of the low alloy steel in the alternating condition was accelerated.

JAEA Reports

Report of the erosion-corrosion of metallic materials under solid-liquid two phase flow

Otani, Kyohei; Sato, Tomonori; Kaji, Yoshiyuki; Yamamoto, Masahiro

JAEA-Review 2019-007, 15 Pages, 2019/06

JAEA-Review-2019-007.pdf:2.35MB

Metallic pipes under solid-liquid two phase flow is damaged by collision of solid particle to the pipe walls, and this phenomenon is named "erosion". In the case of the liquid is corrosive solution, further damage is occurred on the pipe walls chemically, and this named "erosion-corrosion". In the Fukushima Daiichi decommissioning project, the fuel debris will be crushed during removal operation of the debris and micro debris particles would be generated. It is estimated that the pipes of the circulating cooling system would be damaged under the solid-liquid two phase flow containing fuel debris particles. For the reason, the previous study about erosion and erosion-corrosion of metallic materials under solid-liquid two phase flow was surveyed. The survey showed that the damage rate by erosion and erosion-corrosion is influence by a lot of parameter in comparison to the corrosion rate which occurred in no-flow solution. Therefore, it is necessary to pay attention to selecting the experimental method and condition before the investigation about erosion-corrosion of metallic materials under solid-liquid two phase flow is carried out.

Journal Articles

Role of metal cations on corrosion of coated steel substrate in model aqueous layer

Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*

ISIJ International, 58(9), p.1616 - 1622, 2018/09

 Times Cited Count:2 Percentile:72.51(Metallurgy & Metallurgical Engineering)

To elucidate the role of Zn$$^{2+}$$ on corrosion of coated steel, the effects of metal cations on the corrosion of carbon steel in the concentrated Cl$$^{-}$$ aqueous solutions were studied by immersion tests, surface analysis and electrochemical tests. Among the examined metal cations, Zn$$^{2+}$$ showed the significant effect on corrosion inhibition of carbon steel in the Cl$$^{-}$$ aqueous solution at high concentration. XPS analysis results elucidated that Zn$$^{2+}$$ can remain on the steel surface after immersed in the solutions with Zn$$^{2+}$$. EIS measurements showed higher impedance in the solution with Zn$$^{2+}$$ than other solutions, and the results suggested that Zn$$^{2+}$$ reduced the defect points in the thin oxide film by forming a metal cation layer. Based on the experimental results, Zn$$^{2+}$$ may form a layer on the oxide film that protects the Cl$$^{-}$$ attack in the solution. The findings demonstrated that the formation of Zn layer on the oxide film is one of the main reason for showing high and longtime corrosion resistance of Zn coated steel substrate.

Journal Articles

Corrosion inhibition effects of metal cations on SUS304 in 0.5 M Cl$$^{-}$$ aqueous solution

Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*

Corrosion Science, 140, p.8 - 17, 2018/08

 Times Cited Count:6 Percentile:40.49(Materials Science, Multidisciplinary)

The corrosion characteristics of SUS304 exposed to 0.5M Cl$$^{-}$$ aqueous solution containing different metal cations were studied with immersion tests, surface analysis and electrochemical tests. The mechanism of corrosion with metal cations was clarified by the XPS analysis results together with the hard and soft acid and base (HSAB) concept and the passive films structure. It is supposed that metal cations with large hardness make a layer by chemical bonding with the passive films. The passive films are protected by the metal cation layer from Cl$$^{-}$$ attack, and consequently corrosion reactions are inhibited.

Oral presentation

Corrosion behavior changes of A3003 by metal cations in solutions

Otani, Kyohei; Sakairi, Masatoshi*; Kaneko, Akira*

no journal, , 

The effects of metal cations on corrosion of A3003 aluminum alloy in model fresh water were investigated by electrochemical techniques and immersion tests. The electrochemical and immersion results showed that hardness of metal cation, X is not suitable as a corrosion indicator of A3003. A novel corrosion indicator is proposed, and it is shown that the novel indicator can estimate the corrosion rate of A3003 in fresh water.

Oral presentation

Structure of the iron rust layer formed in air-solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi

no journal, , 

Previous study reported that corrosion rate of steel under gas/aqueous alternating condition is three times faster than under solution condition. In this study, the mechanism of corrosion acceleration of steel under gas/aqueous alternating condition was clarified by cross-sectional observation and analysis. The cross-sectional image of the rust layer shows that the layer was composed of multi-layer structure and the chemical analysis of Raman spectroscopy clarified that outer layer is FeOOH and inner layer is Fe$$_{3}$$O$$_{4}$$. These results suggest that FeOOH is formed on the rust initially, and then FeOOH changes to Fe$$_{3}$$O$$_{4}$$ by cathodic reduction reaction. On the other hand, Cl ions concentrated at the rust/metal interface, therefore, anodic Fe dissolution would be accelerated by the concentration of Cl ions. From these reasons, the corrosion of steel under gas/aqueous alternating condition would be accelerated by the cathodic reduction reaction and the anodic Fe dissolution.

Oral presentation

Effects of zinc ion concentration on the surface film structure of mild steel in aqueous solution with chloride ion

Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*

no journal, , 

In the previous study, it was founded that Zn$$^{2+}$$ significantly inhibited the corrosion of mild steel in Cl$$^{-}$$ aqueous solution at room temperature. It is still not fully elucidated the corrosion inhibition ability of Zn$$^{2+}$$ concentration on the steel in Cl$$^{-}$$ aqueous solutions. In the present study, the effects of Zn$$^{2+}$$ concentration on the corrosion inhibition of mild steel were investigated by immersion tests. From the immersion tests, it was found that mass change of specimen closely related to the Zn$$^{2+}$$ concentration in the solutions. SEM images showed that the numbers of pits are decreasing with increasing the Zn$$^{2+}$$ concentration. XPS and AES results showed that Zn$$^{2+}$$ existed as hydroxides by forming a layer with the surface film and the coverage of the layer is increased with increase in Zn$$^{2+}$$ concentration.

Oral presentation

Role of zinc ion on corrosion of metals in aqueous solution

Sakairi, Masatoshi*; Otani, Kyohei; Islam, M. S.*

no journal, , 

Previous studies showed that zinc ion shows higher corrosion resistant property on corrosion of metals in aqueous environment. It is, however, not fully elucidate role of zinc ions on corrosion inhibition of metals in aqueous environments. In this study, the effects of zinc ion on corrosion behavior of aluminum alloy and steels in aqueous environments. From electrochemical and surface analysis results, zinc ion may forms a very effective shielding film which can block the electrochemical reactions, consequently lowers the corrosion rate.

Oral presentation

Study of the accelerated corrosion of carbon steel in air-solution alternating environment, 2; Iron rust structure and the acceleration mechanism

Otani, Kyohei; Tsukada, Takashi; Ueno, Fumiyoshi; Yamamoto, Masahiro

no journal, , 

It has been reported that the corrosion rate of carbon steel in air-solution alternating environment, however, the mechanism of the accelerated corrosion of carbon steel in the alternating environment has not been clarified. In the present study, the mechanism of accelerated corrosion of carbon steel in the alternating condition is investigated by the cross-sectional observation and analysis for rust layer formed on the steel after the corrosion tests. The observation and analysis showed that the multi-layered rust layer was formed on the steel in the alternating environment, and the multi-layer rust layer accelerated the cathodic reaction. This acceleration of the cathodic reaction is the reason why the corrosion rate of carbon steel was accelerated in air-solution alternating environment.

Oral presentation

Study of the accelerated corrosion of carbon steel in air-solution alternating condition, 1; Effect of the concentration of diluted seawater

Tsukada, Takashi; Otani, Kyohei; Terakado, Hiroshi*; Ebata, Koei*; Ueno, Fumiyoshi

no journal, , 

As reported previously, corrosion behavior of carbon steel in the artificial diluted seawater has been examined by the rotating-type corrosion test method and the corrosion rate was accelerated from 3-5 times by the air-solution alternating condition. In this study, an effect of the concentration of diluted seawater at 30$$^{circ}$$C will be presented.

Oral presentation

Computational approach for mechanisms of hydrogen absorption into metal

Igarashi, Takahiro; Otani, Kyohei; Ueno, Fumiyoshi

no journal, , 

Hydrogen embrittlement is one of cause of decrease in the strength of steel due to hydrogen into steel. Although much research has been conducted on the hydrogen embrittlement, the detailed mechanism has not been surely understood yet. In this study, first we assumed that cations in aqueous solution inhibit the hydrogen penetration path to iron, adsorption potential of each metal cation on iron surface were analyzed by first principle calculation with solution approximation. As a result, various cation adsorption potentials were larger in order of Na, Mg, Zn and Al. It was suggested that inhibition ability of hydrogen permeation improves in the order of Na, Mg, Zn and Al. By density of state analysis, it was suggested that the adsorption potential of cation was related to the presence of the combined hybrid orbital generation between cation and Fe.

Oral presentation

The Accelerated corrosion of carbon steel in air-solution alternating condition

Otani, Kyohei; Tsukada, Takashi; Terakado, Hiroshi*; Ebata, Koei*; Ueno, Fumiyoshi

no journal, , 

Inner components of the primary containment vessels (PCVs) in Fukushima Daiichi Nuclear Power Station was observed by remote-controlled robots and the observation showed that carbon steels of the PCVs wall above the contaminated water level was exposed to an air-solution alternating condition. Previous studies have reported that the corrosion rate of carbon steel is accelerated in case of the steel with thin water film exposed in air under the dry/wet condition. This suggests that the corrosion rate of carbon steel will be accelerated in the air-solution alternating condition. However, the corrosion rate of the steel on the corrosion tests which simulated the air-solution alternating condition has not been clarified. In the present study, a novel corrosion test of carbon steel which simulated the air-solution alternating condition was carried out. In order to simulate the alternating condition in the novel corrosion test, the carbon steel was alternately exposed to air and solution by rotating in a water tank which was not completely filled with solution. The surface observations showed that the rust layer formed on the steel after the tests in the alternating condition was thicker than that of the steel rotated always in solution. The mass loss measurements showed that the corrosion rate of carbon steel in the alternating condition was more than three times larger than that of the steel rotated always in solution. A thin water film was confirmed on the steel when the specimen exposed to the air during the tests. It has been reported that the mass transfer of dissolved oxygen to the carbon steel surface is accelerated in case of the carbon steel covered by a thin water film and corrosion of carbon steel is accelerated by the acceleration of oxygen reduction reaction (cathodic reaction). This suggests that the accelerated corrosion of the steel in the alternating condition would be caused by the thin water film on the steel during the tests.

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.

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