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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 (
-FeOOH), rust crust layer (Fe
O
), 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.
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.
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 (FeO), inner crystal (FeO), 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.
*; Nagano, Tetsushi; *
Anatoria Kokogaku Kenkyu, Vol.2 (Kaman, Karehoyukku 2), p.15 - 24, 1993/00
no abstracts in English
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 FeO. These results suggest that FeOOH is formed on the rust initially, and then FeOOH changes to FeO 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.
