Effect of Compacted Bentonite on the Corrosion behavior of Carbon Steel as Geological Isolation Overpack Material

1990 ◽  
Vol 212 ◽  
Author(s):  
A. Honda ◽  
T. Teshima ◽  
K. Tsurudome ◽  
H. Ishikawa ◽  
Y. Yusa ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Sea Water ◽  
Test Period ◽  
Dry Density ◽  
Compacted Bentonite ◽  
Influence Of Temperature On ◽  
Order Of Magnitude ◽  
Average Corrosion Rate

ABSTRACTThe corrosion rate of carbon steel in compacted bentonite was evaluated with regard to the test period length, temperature, chemicals of solution and bulk density of compacted bentonite.The average corrosion rate decreased gradually with increasing test period up to 180 days in immersion tests. The corrosion rate of carbon steel in compacted bentonite at a dry density of 1.32g/cm3 was estimated to be about 0.01 mm/y which was one order of magnitude lower than that in bentonite slurry. No significant influence of temperature on corrosion rates was observed in compacted bentonite in the range of 50∼180 °C. Variation of kinds and concentration of anion(chloride, floride, sulfate, and carbonate)in aqueous solution did not have much influence on the corrosion rate of carbon steel.Immersion tests of carbon steel in compacted bentonite at a dry density of 0.69 ∼ 1.32 g/cm3, which was mixed with an aqueous solution(synthetic sea water and distilled water), were carried out. The corrosion rate in compacted bentonite decreased from 0.04 to 0.005mm/y as the density of bentonite increased.This result suggests that the corrosion rate of carbon steel in compacted bentonite is governed by the diffusivity of corrosive materials. In general, oxygen is the dominate factor affecting corrosion rate, therefore prediction of the average corrosion rate of carbon steel was carried out on the basis of the diffusion behavior of dissolved oxygen in compacted bentonite. The prediction agreed with experimental results.

Migration Behavior of Ferrous Ions in Compacted Bentonite Under Reducing Conditions Using Electromigration

2004 ◽  
Vol 824 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Xiaobin Xia ◽  
Yoshiro Kikuchi ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Electrical Potential ◽  
Infiltration Rate ◽  
Corrosion Products ◽  
Ferrous Ion ◽  
High Level Waste ◽  
Dry Density ◽  
Compacted Bentonite ◽  
Buffer Material

AbstractCarbon steel is one of the candidate overpack materials for high-level waste disposal and is expected to assure complete containment of vitrified waste glass during an initial period of 1000 years in Japan. The lifetime of the carbon steel overpack will depend on its corrosion rate. The corrosion rate of carbon steel is reduced by the presence of buffer material such as bentonite. Buffer material will delay the supply of corrosive materials and discharge of corrosion products through it. Carbon steeloverpack will be corroded by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. Therefore, it is important to study the migration of iron corrosion products through the buffer material because it may affect the corrosion rate of overpack, migration of redox-sensitive radionuclides, and the properties of the buffer material. Electromigration experiments have been carried out with source of iron ions supplied byanode corrosion of iron coupon in compacted bentonite. The carbon steel coupon was connected as the working electrode to the potentiostat and was held at a constant applied potential between - 200 to 1000 mV vs. Ag/AgCl electrode for 48 hours. Corrosion currents were 0.5 to 2mA initially and depended on the supplied electrical potential, then decreased to approximately 0.1 mA in a few hours. The final corrosion current was independent of supplied electrical potential. It is expected that iron ion could migrate as ferrous ion through interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. The rate-determining process of this experimental configuration could be infiltration rate of ferrousioninto bentonite. Infiltration rate of ferrous ion into bentonite was increasing with dry density of bentonite.

Diffusion of Uranium in Compacted Bentonite in the Presence of Carbon Steel

1993 ◽  
Vol 333 ◽  
Author(s):  
K. Idemitsu ◽  
H. Furuya ◽  
Y. Tachi ◽  
Y. Inagaki
Keyword(s):  
Carbon Steel ◽  
Pore Water ◽  
Silica Sand ◽  
High Level Waste ◽  
Dry Density ◽  
Compacted Bentonite ◽  
Reducing Conditions ◽  
Order Of Magnitude ◽  
The Difference ◽  
High Level

ABSTRACTIn a high-level waste repository, a carbon steel overpack will be corroded by consuming oxygen trapped in the repository after closure. This will create a reducing environment in the vicinity of repository. Reducing conditions are expected to retard the migration of redox-sensitive radionuclides such as uranium.The apparent diffusivities of uranium were measured in compacted bentonite (Kunigel VI®, Japan) in contact with carbon steel under reducing conditions or without carbon steel under oxidizing conditions for comparison. The apparent diffusivities of uranium were 3.5 × 10-14 to 1.1 × 10-13 m2/s under reducing conditions and 9.0 × 10-13 to 1.4 × 10-12 m2/s under oxidizing conditions. There was no significant effect of dry density (1.6 to 1.8 g/cm3) and silica sand (0 or 40%) on the apparent diffusivities.Since the bentonite pore water would be buffered at a pH between 8 and 9, uranium in the bentonite pore water would probably exist as a neutral hydroxide complex under reducing conditions and as an anioníc carbonate or hydroxide complex under oxidizing conditions. The anion exclusion theory cannot explain the difference of diffusivities between the two conditions. The uranium concentrations in bentonite under oxidizing conditions were one order of magnitude higher than those under the reducing conditions. The uranium concentration in the bentonite pore water under the reducing condition is estimated to be two orders of magnitude lower than that under the oxidizing conditions under the assumption of diffusion in porous media.

Enhancement of Borosilicate Glass Dissolution by Silica Sorption and Diffusion in Compacted Bentonite: A Model Study.

1990 ◽  
Vol 212 ◽  
Author(s):  
Enzo Curti ◽  
P. A. Smith
Keyword(s):  
Corrosion Rate ◽  
Acid Concentration ◽  
Silicic Acid ◽  
Computer Code ◽  
Glass Block ◽  
Concentration Gradients ◽  
Compacted Bentonite ◽  
Glass Corrosion ◽  
Model Study ◽  
Average Corrosion Rate

ABSTRACTExperimental evidence indicates that glass corrosion rates decrease proportionally with the increase of silicic acid concentration in the solution contacting the glass surface. A minimum corrosion rate (Rsat) is reached when the solution becomes saturated with respect to an unidentified amorphous siliceous compound. In a repository where the vitrified waste form is surrounded by compacted bentonite, the silica dissolved from the glass will diffuse into the pore solution and concentration gradients will be established throughout the backfill material. The silicic acid concentration at the glass-bentonite interface, and thus the glass corrosion rate, will then be diffusion controlled. Moreover, experimental work suggests that significant sorption of silica by clay minerals in bentonite may accelerate glass corrosion.A model describing glass corrosion coupled with diffusive transport and sorption of silica in bentonite has been developed and incorporated in a FORTRAN computer code (GLADIS). The model assumes: (a) a linear isotherm for the sorption of silica (KD), (b) time and space invariant pH, temperature and ionic strength, (c) proportionality between the quantity of silica precipitated and the amount of glass dissolved and (d) cylindrical geometry. Preliminary calculations with a particular parameter set at 90°C, assuming no silica sorption on the bentonite, indicate for an unfractured glass block that a stationary state is rapidly reached in which the silica concentration at the glass-bentonite interface is lower than the saturation concentration. This implies that the glass corrodes at a more rapid rate than Rsat (RsS ∼ 8 Rsat) If moderate silica sorption is assumed (KD = 0.5 m3 kg−1), the attainment of stationary conditions is delayed by the removal of silicic acid from solution, and the average corrosion rate is further increased by a factor ∼ 2.

Migration Behaviour of Lanthanides in Compacted Bentonite with Iron Corrosion Product Using Electrochemical Method

2012 ◽  
Vol 1475 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Daisuke Akiyama ◽  
Yoshihiko Matsuki ◽  
Yusuke Irie ◽  
Yaohiro Inagaki ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Dispersion Coefficient ◽  
Reference Electrode ◽  
High Level Waste ◽  
Dry Density ◽  
Migration Behavior ◽  
Iron Corrosion ◽  
Compacted Bentonite ◽  
Steel Coupon ◽  
Best Fit

ABSTRACTAfter the closure of a high-level waste repository, corrosion of the carbon steel overpack will occur. The corrosion products can then migrate into bentonite and affect the migration behavior of radionuclides in bentonite. Therefore, electrochemical experiments, with Fe2+ supplied by anodic corrosion of carbon steel, were carried out to study trivalent lanthanides in compacted bentonite. The interface between a carbon steel coupon and bentonite (dry density, 1.5 Mg/m3) was spiked with a tracer solution containing Nd(NO3)3, Eu(NO3)3, Dy(NO3)3, and Er(NO3)3. The carbon steel coupon was connected as the working electrode to a potentiostat and held at a constant potential between -550 and 0 mV (vs. Ag/AgCl reference electrode) for 7 days. A model using dispersion and electromigration could explain the measured profiles in the bentonite specimens. The best-fit electromigration velocity was related to the applied electric potential and was 1.0–3.8 nm/s for Nd, Eu, Dy, and Er ions. For these lanthanides, the best-fit dispersion coefficient was also related to the applied potential and was 0.8–1.6 μm2/s, and the dispersion length was calculated as 0.2 mm from the linear relationship between the dispersion coefficient and electromigration velocity. Finally, the apparent diffusion coefficient for these lanthanides was estimated as 0.6–0.9 μm2/s.

Effect of Flow Velocity of Sea Water on Corrosion Rate of Low Carbon Steel

2015 ◽  
Vol 799-800 ◽  
pp. 232-236 ◽  
Author(s):  
Abd Alrahim Al Shikshak ◽  
Abd Alhakem Mansour ◽  
A. Taher
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Flow Velocity ◽  
Sea Water ◽  
Low Carbon Steel ◽  
Rate Data ◽  
Low Carbon ◽  
Solution Composition ◽  
Saline Environment ◽  
Very High

The purpose of this research is to investigate the corrosion rate of low carbon steel in saline environment. The influence of variety of conditions that represent the actual conditions in practice such as the flow velocity and solution composition, particularly Na+, Cl-and SO4-2, content were performed. Weight loss test of low carbon steel in the lab was conducted to determine the corrosion rate data in stagnant and flowing seawater for comparison to investigate the effect of flow velocity of sea water on the corrosion behavior of the low carbon steel. Results show that the corrosion rate of low carbon steel is increased by increasing the flow of seawater, but at very high velocities the corrosion rate was recorded to be decreased. XRD results show that the corrosion products contain both Fe2O3and FeO(OH).

scholarly journals Influence of the electromagnetic field on the corrosion of low-carbon steel in aqueous mineralized media and on the crystallization of calcium carbonate in the presence of iron(II) ions

2021 ◽  
pp. 116-124
Author(s):  
S.R. Alimbekov ◽  
◽  
F.G. Ishmuratov ◽  
V.V. Nosov ◽  
A.I. Voloshin ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Electromagnetic Field ◽  
Calcium Carbonate ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Low Carbon Steel ◽  
Iron Ions ◽  
Low Carbon ◽  
Near Surface ◽  
Salt Deposition

The influence of the electromagnetic field (EMF) on the corrosion of structural carbon steel in a 3% aqueous solution of sodium chloride in the presence of CO2 was studied. It is shown that the EMF increases the corrosion rate of steel by 1.13 times in a 3% aqueous solution of NaCl in the presence of CO2. When Ca2+ ions are added to the solution, the corrosion rate of steel decreases under the influence of an electromagnetic field. It is assumed that the formation of CaCO3 in the near-surface layer of the solution and its adsorption on the metal surface prevents the development of corrosion. The influence of the electromagnetic field generated in the frequency range from 100 to 200 kHz on the crystallization of CaCO3 from supersaturated aqueous solutions on the model system CaCl2 – NaHCO3 – FeSO4 is studied. It was found that Fe2+, rather than EMF, has a more significant effect on salt deposition. The efficiency of the effect of Fe2+ on the inhibition of salt deposition in the model of mineralized water CaCl2-NaHCO3 is 11.5% higher than when exposed to EMF. During the crystallization of CaCO3, the predominant formation of aragonite is observed. In the presence of iron ions and under the influence of EMF, there was a decrease in the formation of aragonite and an increase in the formation of calcite and vaterite. Keywords: electromagnetic field; corrosion; carbon steel; iron ions; scale deposition; crystallization; calcium carbonate.

scholarly journals Corrosion Study of Carbon Steel in Carbonated BUMEA-2EE Nonaqueous Solution

2021 ◽  
Vol 2076 (1) ◽  
pp. 012057
Author(s):  
Fang Liu ◽  
Xiaoqian Du ◽  
Lemeng Wang ◽  
Dong Fu
Keyword(s):  
Aqueous Solution ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Mass Fraction ◽  
Nonaqueous Solution ◽  
Influence Of Temperature ◽  
Corrosion Study ◽  
Equipment Corrosion ◽  
Polarization Behaviour

Abstract Different effort has been attempted to reduce the equipment corrosion of CO2 absorption using chemical solvents. In this paper, the corrosion of carbon steel in carbonated 2-(butylamino)ethanol (BUMEA)-2-ethoxyethanol (2EE) non-aqueous solution was studied by using a CHI602E electrochemical analyser. The polarization behaviour and corrosion rate of carbon steel in non-aqueous blends of BUMEA-2EE were investigated. The influence of temperature, the mass fraction of BUMEA (wBUMEA) and CO2 loading (α) on the corrosion rate were clarified.

Various Size of Glass Fiber Treated Silane Coupling Agent in Epoxy Primer Coating: Corrosion Behaviour

2019 ◽  
Vol 947 ◽  
pp. 137-141
Author(s):  
Zuliahani Ahmad ◽  
Hasniraaiman ◽  
Munirah Onn ◽  
Ahmad Faiza Mohamad ◽  
Muhamad Adib Ikhwan ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Corrosion Rate ◽  
Glass Fiber ◽  
Silane Coupling Agent ◽  
Steel Plate ◽  
Sea Water ◽  
Glass Fibers ◽  
Optimum Size ◽  
Epoxy Primer ◽  
Silane Coupling

The epoxy primer coatings with various size of treated glass fiber was successfully developed using hand brushing technique on carbon steel plate. The glass fibers used were treated with silane coupling agent, 3-aminopropyl triethoxysilane. The Fourier Transform-Infared Spectroscopy (FTIR) affirmed the presence of silanol group at 1221.12cm-1 .Hence, the primer coating was prepared with three different sizes of treated glass fiber (45, 150, and 250 μm) and the corrosive properties has been studied. The corrosion rate was determined using Tafel plot and the immersion test was done in 3.5% NaCl and sea water for 9 days. Formulation of epoxy resin-GF-45μm displayed the optimum size to reduce the corrosion rate of epoxy primer coatings at 8.3713 mm/year and polarization resistance was the highest at 107.48Ω which indicates that epoxy coating have higher resistance towards corrosion, coating adherence and there was formation of more protective film on steel.Whilst immersion in 3.5% NaCl solution and sea water followed the same trend with 45 μm exhibited the less corrosive behavior for 9 days exposure. When the solution penetrated into the coating, the ultra-short glass fibers prevent the water from permeating and prolong the water diffusion path. Thus, it provided good anti-corrosive properties for formulation 2 at 45μm GF. In conclusion, the size of GF plays an important role in determining the corrosive behavior of epoxy primer coatings. The optimum size of GF at 45 μm proved to diminish the corrosiveness of carbon steel plate.

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