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.
Omori, Atsushi*; Akiyama, Eiji*; Abe, Hiroshi*; Hata, Kuniki; Sato, Tomonori; Kaji, Yoshiyuki; Inoue, Hiroyuki*; Taguchi, Mitsumasa*; Seito, Hajime*; Tada, Eiji*; et al.
Zairyo To Kankyo, 69(4), p.107 - 111, 2020/04
To evaluate the effect of oxidants, which are formed by radiolysis of water under gamma ray irradiation, on the corrosion of a carbon steel in humid environment, ozone was introduced as a model oxidant in to humidity-controlled air at 50C in a thermo-hygrostat chamber. Corrosion monitoring was performed by using an Atmospheric Corrosion Monitor-type (ACM) sensor consisting of a carbon steel anode and an Ag cathode. The output current of the ACM sensor was increased with the increase in relative humidity and it was obviously increased with the increase in the introduced ozone concentration at each relative humidity. The results indicate that ozone accelerates the corrosion of the carbon steel. The effect of ozone on the corrosion acceleration is attributed to the fast reduction reaction and fast dissolution reaction in to water compared to that of oxygen.
Islam, M. S.*; Otani, Kyohei; Sakairi, Masatoshi*
ISIJ International, 58(9), p.1616 - 1622, 2018/09
To elucidate the role of Zn 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 showed the significant effect on corrosion inhibition of carbon steel in the Cl aqueous solution at high concentration. XPS analysis results elucidated that Zn can remain on the steel surface after immersed in the solutions with Zn. EIS measurements showed higher impedance in the solution with Zn than other solutions, and the results suggested that Zn reduced the defect points in the thin oxide film by forming a metal cation layer. Based on the experimental results, Zn 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.
Haruna, Takumi*; Miyataki, Yuki*; Hirohata, Yohei*; Shibata, Toshio*; Taniguchi, Naoki; Tachikawa, Hirokazu*
Zairyo To Kankyo, 67(9), p.375 - 380, 2018/09
This research aimed to confirm the formation of FeO film on Fe immersed in aqueous 45 mass% NaOH solution containing some oxidants at the boiling temperature, to recognize the optimum immersion time for the formation of thick and protective film, and to reveal the absorption behavior of DO in the FeO film at room temperature. The results were obtained as follows. It was confirmed that FeO film was formed on Fe immersed in the NaOH solution for a time more than 0.6 ks, and the film thickness increased parabolically with an increase in the immersion time. DO absorption test was carried out to the films formed in the NaOH solution for immersion times of 1.2 and 3.6 ks. An amount of DO absorbed into the film increased with an increase in an absorption time up to 1000 ks, and an absorption time more than 1000 ks made an amount of DO constant. The constant amount of DO was larger for the film formed on Fe immersed in the NaOH solution for 3.6 ks than that for 1.2 ks. The transient of the amount of DO absorbed into the film was analyzed on the basis of Fick's law for diffusion, and diffusion coefficients of DO were obtained to be 5.110 cm s and 9.910 cm s for the films formed for 1.2 and 3.6 ks, respectively. Therefore it was estimated that the diffusion coefficient of the FeO film was in the region from 5.110 cm s to 9.910 cm s.
Yamamoto, Masahiro; Komatsu, Atsushi; Sato, Tomonori; Nakano, Junichi; Ueno, Fumiyoshi
Proceedings of 17th Asian Pacific Corrosion Control Conference (APCCC-17) (USB Flash Drive), 8 Pages, 2016/01
In Fukushima-Daiichi Nuclear Power Station, decommissioning procedures are continuing more than 30 years until fuel debris removal. It is important to keep soundness of primary container vessel (PCV), made of carbon steel, during these procedures. Corrosion of carbon steel is well-known to be controlled by cathodic reaction, in usual, oxygen reduction reaction. Corrosion of carbon steel could be mitigated by nitrogen injection procedure. However, a lot of radioactive materials exist in cooling water, an effect of radiolysis product on corrosion is an important problem. Clarifying an irradiation effect for corrosion of carbon steel, corrosion test was conducted in Co -ray irradiated condition. Electrochemical measurements were conducted to determine cathodic current density of samples. Corrosion rates of carbon steel decrease with time in both -ray irradiated and non-irradiated conditions. Measured values of cathodic current density gradually decreased with time and then stayed at constant value.
Motooka, Takafumi; Ueno, Fumiyoshi
Zairyo To Kankyo, 64(6), p.220 - 223, 2015/06
Corrosion behavior of carbon steel in chloride aqueous solutions under a low dose rate was investigated by corrosion test using chloride aqueous solutions with different chloride concentration at a dose rate of 500 Gy/h. The corrosion rate of carbon steel increased by the irradiation, and the corrosion rate had the maximum value at a certain chloride concentration. The oxidants produced by radiolysis of chloride aqueous solution enhanced the corrosion of carbon steel. The main oxidants were oxygen and hydrogen peroxide, and the diffusion process of oxidants controlled the corrosion of carbon steel under irradiation. There was a positive correlation between the dependence of corrosion rate and chloride concentration and the dependence of oxidant concentration and chloride concentration.
Koeki Zaidan Hojin Tottoriken Kyoiku Bunka Zaidanhen 2014 "Yoshida Nakamichi Iseki" Tottoriken Kyoiku Iinkai, p.221 - 230, 2015/03
An ancient socketed iron axe was excavated from Yoshida Nakamichi site in Tottori City, Tottori Prefecture. To understand reasons of corrosion state of the axe, we studied relationship between burial environment and corrosion. As environmental conditions, we investigated groundwater chemistry and corrosion rate with iron probe monitor, etc. As for corrosion state, we analysed corrosion depths with a X-ray CT and corrosion products with a portable XRD/XRF. As results, we found that the redox potential and dissolved oxygen level as environmental conditions were very low, and that the maximum corrosion rate (210 mm/y) evaluated from measured corrosion depths was smaller than the probe corrosion rate (510 mm/y) by two orders of magnitude and identified siderite (FeCO) as a corrosion product. The results suggested that the siderite precipitated on the surface of the iron sword inhibited corrosion reaction.
Taniguchi, Naoki; Kawakami, Susumu; *
JNC-TN8400 2001-025, 27 Pages, 2002/03
It is essential to understand the corrosion type of carbon steel under the repository conditions for the lifetime assessment of carbon steel overpack used for geological isolation of high-level radioactive waste. According to the previous study, carbon steel is hard to passivate in buffer material assuming a chemical condition range of groundwater in Japan. However, concrete support will be constructed around the overpack in the case of repository in the soft rock system and groundwater having a higher pH may infiltrate to buffer material. There is a possibility that the corrosion type of carbon steel will be influenced by the rise of the pH in groundwater. In this study, anodic polarization experiments were performed to understand the passivation condition of carbon steel in buffer material saturated with water contacted with concrete. An ordinary concrete and a low-alkalinity concrete were used in the experiment. The results of the experiments showed that the carbon steel can passivate under the condition that water having pH 13 infiltrate to the buffer material assuming present property of buffer material. If the low-alkalinity concrete is selected as the support material, passivation can not occur on carbon steel overpack. The effect of the factors of buffer material such as dry density and mixing ratio of sand on the passivation of carbon steel was also studied. The results of the study showed that the present property of buffer material is enough to prevent passivation of carbon steel.
Inoue, Kazuko*; Nakamura, Hiroshi*; Horikawa, Takeshi*; Kawashima, Hisakazu*; Tsujikami, Tetsuya*; Minakawa, Nobuaki
Nippon Zairyo Gakkai Dai-50-Ki Gakujutsu Koenkai Koen Rombunshu, p.415 - 416, 2001/05
no abstracts in English
Taniguchi, Naoki; Kawasaki, Manabu*; Fujiwara, Kazuo*
JNC-TN8400 2001-011, 62 Pages, 2001/03
The corrosion of metallic materials used in natural environment are sometimes affected by microbial action. It is apprehended that microorganism living in deep underground or brought from ground surface during excavation makes an impact on overpack material for geological disposal of high-level radioactive waste. Sulfate reducing bacteria (SRB) is known to be one of the most representative microorganism which affects the corrosion of metals. In this study, the behavior of growth of SRB was investigated at first under the presence of bentonite as a main component of buffer material which encloses the overpack. The results of the tests showed that the population of SRB after the culture in synthetic sea water mixed with bentonite decreased with increasing the ratio of bentonite/solution. SRB was hardly grown in medium whose bentonite/solution ratio exceeded 1000g/l. As a conservative case, the effects of sulfide on the corrosion of overpack materials were also studied assuming high activity of SRB. Carbon steel, copper and titanium specimens were immersed in synthetic sea water purging 0.1MPa HS gas and the corrosion behavior was compared with the results in N gas purging environment. Obvious effect of sulfide on the corrosion of carbon steel was not observed, but the corrosion rates of copper specimens were accelerated several hundred times by purging HS gas. The absorption of hydrogen into titanium specimens was not affected by purging HS gas, but the difference of hydrogen absorption between pure titanium and titanium alloy containing 0.06%-Pd was observed.
Taniguchi, Naoki; ; Kawasaki, Manabu*; Masugata, Tsuyoshi*
JNC-TN8400 2001-001, 56 Pages, 2000/12
It is necessary to clear the effects of corrosion products on the corrosion life time of carbon steel overpack for geological isolation of high-level radioactive waste(HLW). Especially, it is important to understand the effects of magnetite because magnetite as a simulated corrosion product is reported to accelerate the corrosion rate of carbon steel. In this study, corrosion tests to reproduce the acceleration of corrosion due to magnetite was performed and the mechanism of the acceleration was investigated to evaluate the effects of magnetite as a corrosion product. Based on the results of experiments, following conclusions are obtained ; (1)Magnetite powder accelerates the corrosion rate of carbon steel. The main reaction of corrosion under the presence of magnetite is the reduction of Fe(III) in magnetite to Fe(II), but the reaction of hydrogen generation is also accelerated. The contribution of hydrogen generation reaction was estimated to be about 30% in the total corrosion reaction based on the experimental result of immersion test under the presence of magnetite. (2)Actual corrosion products containing magnetite generated by the corrosion of carbon steel protect the metal from the propagation of corrosion. The corrosion depth of carbon steel overpack due to magnetite was estimated to be about 1 mm based on the results of experiments. Even if the effect of magnetite is taken into the assessment of corrosion lifetime of overpack, total corrosion depth in 1000 years is estimated to be 33 mm, which is smaller than the corrosion allowance of 40 mm described in the second progress report on research and development for the geological disposal of HLM/ in Japan. It was concluded that the effect of magnetite on the corrosion life time of carbon steel overpack is negligible.
; ; Ohno, Shuji;
JNC-TN9400 2000-092, 247 Pages, 2000/08
Small-scale sodium pool combustion tests Run-F7-3 and Run-F8-1 were performed to investigate the corrosion of floor liner under high moisture condition. ln the both tests, which were performed using the 3m FRAT-1 vessel at the SAPFIRE facility, the sodium of 507deg-C was leaked on the carbon steel catch pan about for 25 minutes with the flow rate of around 25 kg/h. The air in the vessel was ventilated with the flow rate of 5m/min containing the moisture of 25000-28000 vol.ppm. The duration of combustion was different in two tests by changing the starting time of argon gas injection into the vessel. As the results of post-test analysis such as observation of catch pan surface and chemical analysis of the deposits, it was confirmed that 'Na-Fe double oxidization type corrosion' was dominant in the both tests and that the catch pan and deposits were not under the condition leading to the occurrence of 'molten salt type corrosion.'
Harada, Yuhei; Maruyama, Yu; Maeda, Akio*; Chino, Eiichi; Shibazaki, Hiroaki*; Kudo, Tamotsu; Hidaka, Akihide; Hashimoto, Kazuichiro; Sugimoto, Jun
Journal of Nuclear Science and Technology, 37(6), p.518 - 529, 2000/06
no abstracts in English
Akashi, Masatsune*; Fukaya, Yuichi*; Asano, Hidekazu*
JNC-TJ8400 2000-015, 46 Pages, 2000/02
Difference of hydrogen generation phenomena on the surface of the Steels were not observed between carbon steel, atmospheric corrosion resisting steel and 5%-Ni steel. Rust layer was formed on these three-type of steels by steam oxidation method. And the chemical composition of the rust for the steels were basically two (2) layers structure for the previous two steels as hematite (FeO) based for the outer layer and magnetite (FeO) based for the inner layer. And for the last steel, it had three (3) layer in the rust as hematite (FeO) based for the outer layer, magnetite (FeO) based for the intermediate layer and Ni based layer for the inner layer. These steels showed mostly same Tafel gradient in their cathodic polarization curves compare with that for no rust specimens. However, the exchange current density which reaction is assumed as a hydrogen generation reaction was largely increased. The cathodic reaction for each steels whose surface is covered by magnetite layer might be accelerated, then the corrosion rate was considered as accelerated, too.
Akashi, Masatsune*; Fukaya, Yuichi*; Asano, Hidekazu*
JNC-TJ8400 2000-014, 22 Pages, 2000/02
Difference of hydrogen generation phenomena on the surface of the Steels were not observed between carbon steel, atmospheric corrosion resisting steel and 5%-Ni steel. Rust layer was formed on these three-type of steels by steam oxidation method. And the chemical composition of the rust for the steels were basically two(2) layers structure for the previous two steels as hematite(FeO) based for the outer layer and magnetite(FeO) based for the inner layer. And for the last steel, it had three(3) layer in the rust as hematite(FeO) based for the outer layer, magnetite(FeO) based for the intermediate layer and Ni based layer for the inner layer. These steels showed mostly same Tafel gradient in their cathodic polarization curves compare with that for no rust specimens. However, the exchange current density which reaction is assumed as a hydrogen generation reaction was largely increased. The cathodic reaction for each steels whose surface is covered by magnetite layer might be accelerated, then the corrosion rate was considered as accelerated, too.
Shibata, Toshio*; *; *; Tsuru, Toru*; Inoue, Hiroyuki*
JNC-TJ8400 2000-013, 38 Pages, 2000/02
JNC-TJ8400 2000-009, 138 Pages, 2000/02
To evaluate corrosion behavior of carbon steel, a candidate materials of overpack, buried in soil for a long time, the water pipes buried in freshwater clay for a long time we digged out and the soil environment and the corrosion weight loss of pipes have been researched. From the results, a corrosion model (an empirical equation), an oxygen reduction reaction rate-determing step type, of carbon steel buried in soil was introduced. The corrosion data of under ground pipe collected by the Japan Community Gas Associations was used to increase reliability of the corrosion model equation. These data are one of researches of corrosion behavior of carbon steel buried in soil for a long time studied by at home and abroad. 38 samples buried freshwater clay were selected in 171 samples. With estimating the corrosion velocities and the soil environment factors of the above data, the maximum depth of pit corrosion was calculated by the statistical method of the extreme values using the area of overpack as the recurrent time. The correlation between the soil environment factors and the corrosion weight loss was obtained by the correlation analysis. The corrosion model of the maximum depth of pit corrosion at 0.99 of cumulative probability was compared between the under ground pipe data and the above data. On the reference data and the above data, the corrosion model equation; H = aY was compared with the maximum depth of pit corrosion at 0.99 cumulative probability. The data of water pipes and community gas pipes at 0.99 cumulative probability showed the reasonable values when these data were compared with the reference data. So that the model was proved as a good corrosion model m the neutral low dissolved oxygen environment.
Honda, Takashi*; *
JNC-TJ8400 2000-007, 200 Pages, 2000/02
In general, it is very difficult to evaluate the residual state of metallic iron and the original shape of iron-base archaeological artifacts, as these are covered by thick oxide films formed in the ground during over several hundred years. The purpose of this research is to quantify the corrosion of an artifact such as base, knife, and nail, which was digged out of the relics about 500-1,000 years old. (1)The outer oxide film layer and the inner metallic iron can be quantitatively divided by using X-ray CT method. Furthermore, the original surfaces of artifacts can be estimated from the obtained images, even if the metallic iron has corroded completely. The X-ray CT images were also compared with those obtained by X-ray transmission inspection. (2)The corrosion amounts and rates were evaluated on the basis of thicknesses, densities, and iron concentrations of oxide films. (3)The characteristic differences between ancient iron and modern carbon steel were evaluated by analyzing the ancient iron slag.
Hashizume, Shuji*; Matsumoto, Junko; Bamba, Tsunetaka
Genshiryoku Bakkuendo Kenkyu, 6(1), p.101 - 106, 1999/12
no abstracts in English
*; *; Tanai, Kenji
JNC-TN8400 99-049, 94 Pages, 1999/11
This paper reports the results of design analysis and trial manufacturing of copper-carbon steel composite overpacks. The overpack is one of the key components of the engineered barrier system, hence, it is necessary to confirm the applicability of current technique in their manufacture. The Copper-Carbon steel composite overpack consists of a double container, an outer vessel made of oxygen-free, high-purity copper as the corrosion allowance material, and an inner vessel made of carbon steel as the pressure-resistant material. The trial manufacturing in this time, only the copper outer vessel has been fabricated. Both oxygen-free copper and oxygen-free phosphorus copper were used as materials for the outer vessel. For the shell and bottom portion, these materials were formed integrally by a backward extrusion method. For sealing the top cover plate to the main body, an electron-beam welding method was applied. After manufacturing, mechanical testing of specimens from the copper vessels were carried out. It was confirmed that current technique has sufficient feasibility to manufacture outer vessel. In addition, potential for irradiation embrittlement of the inner carbon-steel vessel by irradiation from vitrified waste over the life time of the overpack has been analyzed. It was shown that the small degree of irradiation embrittlement gives no significant impact on the pressure resistance of the carbon-steel vessel. Future research and development items regarding copper-carbon steel composite overpacks are also discussed.