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

https://doi.org/10.3323/jcorr.70.480

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 (-FeOOH), rust crust layer (FeO), inner crystal (FeO), 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.

The Activity of sulfate reducing bacteria in bentonite and the effect of hydrogen sulfide on the corrosion of candidate materials for overpacks

Taniguchi, Naoki; Kawasaki, Manabu*; Fujiwara, Kazuo*

JNC TN8400 2001-011, 62 Pages, 2001/03

JNC-TN8400-2001-011.pdf:5.67MB

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.

Relation of the corrosion rate of carbon steel in irradiating dilute artificial seawater and the dose rate of dilute artificial seawater

Motooka, Takafumi

no journal, , 

Relation of the corrosion rate of carbon steel in irradiating dilute artificial seawater and the dose rate was investigated by corrosion tests using Co-60 source in the atmospheric condition, quantitative analysis of test solutions and identification of rusts. The corrosion rate of carbon steel was increased with the increase of dose rate of dilute artificial seawater. Hydrogen peroxide formed by water radiolysis controlled the corrosion rate of carbon steel. The oxidation of Fe by oxidizing species formed by water radiolysis affected the rust formation process of the carbon steel.

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 30C will be presented.