The Critical Condition for the Initiation of Localized Corrosion of Mild Steels in Contact with Bentonite Used For Nuclear Waste Package

1991 ◽  
Vol 257 ◽  
Author(s):  
Guen Nakayama ◽  
Masatsune Akashi
Keyword(s):  
Mild Steel ◽  
Nuclear Waste ◽  
Pitting Corrosion ◽  
Natural Water ◽  
Crevice Corrosion ◽  
Water Environment ◽  
Underground Water ◽  
Localized Corrosion ◽  
Critical Conditions ◽  
General Corrosion

ABSTRACTIt has been established that the mild steels which undergo the general corrosion in the acidic to neutral environments, attain the passivity status in alkaline environments, thereby becoming liable to the localized corrosion, such as pitting corrosion and crevice corrosion. Now, for the case of using bentonite as a buffer to stand between the hostrock and the geological disposal packages of high level nuclear waste, localized corrosion behaviors of mild steel as a candidate for such a package has been studied quantitatively for environments where the the otherwise neutral ground water would be turned slightly alkaline with pH = 9.5 - 10.0.In view of the lack of quantitative data on the passivity-to-localized corrosion of mild steel in natural water environments of weak alkalinity, the present authors have previously determined an empirical E-pH diagram for mild steel with a 20 °C, 1 m mol/L [HC03-], 10 ppm [CI -] solution simulating the natural water environment concerned; it has been shown that the general corrosion-to-passivity transition condition was determined to be pHd =9.4, and the mild steel was shown to be liable to localized corrosion over a large portion of the passivity domain. The present paper discusses behaviors, mechanisms, and critical conditions for initiation of localized corrosion in mild steel placed in bentonitesuspending natural water environment, in terms of the critical potentials for pitting (Vc), and crevice corrosion (ER,CREV). Bentonite was addid to the solution in varying amounts to give bentonite-to-solution ratios up to 0.1, while the pHvalue was adjusted appropriately with sodium carbonate, always keeping the bentonite particles in suspension.It is demonstrated that bentonite particles suspended in water will deposit upon the steel on receipt of Fe2 + ions, thereby promoting pitting corrosion by preventing repassivation and promoting crevice corrosion by acting as an effective crevice, once the environment conditions become favorable for localized corrosion.We conclude therefore that disposal package made of mild steel and placed in an underground water environment with bentonite as buffer will be liable to localized corrosion.

The Critical Condition for the Initiation of Localized Corrosion of Mild Steel Used for Nuclear Waste Package

1990 ◽  
Vol 212 ◽  
Author(s):  
Gen Nakayama ◽  
Mastsuna Akashi
Keyword(s):  
Mild Steel ◽  
Crevice Corrosion ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Alkaline Water ◽  
Propagation Behavior ◽  
Neutral Water ◽  
High Level ◽  
Term Performance ◽  
Critical Ph

ABSTRACTThe general corrosion rate of mild steel is so small in neutral water environments that adequately provided corrosion allowance can ensure the requirement of one thousand years’ integrity of geological disposal package of high-level nuclear wastes. In alkaline water environments, however, mild steels can passivate themselves and often undergo localized corrosion in much the same manner stainless steels do in neutral water environments. This paper describes a study of localized corrosion behavior of the mild steel conducted to assess the long-term performance of the disposal packages. The critical potentials for pitting and crevice corrosion and critical pH for general corrosion-to-passivity transition were determined for neutral and alkaline water environments. Effects of temperature, pH, and chloride and other anion concentrations on the critical potentials and the critical pH were discussed. The initiation and propagation behavior of crevice corrosion was also analyzed under potentiostatic conditions.

Development of Corrosion Inhibitors to Mitigate Elemental Sulfur Induced Pitting Corrosion

2021 ◽  
Author(s):  
Douglas C. Dickey ◽  
Nihal U. Obeyesekere Obeyesekere ◽  
Jonathan J. Wylde
Keyword(s):  
Mild Steel ◽  
Pitting Corrosion ◽  
Elemental Sulfur ◽  
Extreme Environments ◽  
Oil And Gas Industry ◽  
Working Environment ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Gas Industry ◽  
High Hydrogen

Abstract The effects of elemental sulfur on the corrosion of mild steel is a serious problem in the oil & gas industry costing millions of dollars annually in lost production and assets. Mitigating the corrosive effects of elemental sulfur on mild steel in the oil and gas industry is a challenge and finding a viable solution would provide a more cost effective and safer working environment and as well as be environmentally conscious. Currently, there are no highly effective products for elemental sulfur corrosion in the marketplace. More than fifty new chemical formulations were blended and screened by rotating cylinder electrode method (RCE). These formulations were tested in the presence of 0.1% elemental sulfur in mildly sour conditions. The promising candidates were identified and tested again in the presence of elemental sulfur under the same mildly sour conditions. The most promising candidates from the initial screening were then subjected to rotating cage autoclave (RCA) testing for extended periods of time in the presence of 0.1% and 0.15% elemental sulfur. The general corrosion rates were calculated via weight loss and the metal surfaces were examined under a high-power digital microscope for pitting and localized corrosion. A detailed analysis of the above testing yields promising results. The results from the testing show that formulations mitigate pitting in environments containing elemental sulfur. In less harsh conditions, such as low chloride brines or low CO2 environment, formulations seem to provide excellent protection against general corrosion while mitigating pitting due to elemental sulfur. In more extreme environments such as harsh brines with elevated chloride levels, high hydrogen sulfide and CO2 levels, the formulations mitigate pitting but need further development in inhibiting general corrosion The best product currently developed inhibits corrosion and pitting in the presence of elemental sulfur in various conditions and performs well against elemental sulfur in more aggressive sour systems. We are currently improving the performance against elemental sulfur and developing chemistries to mitigate polysulfide induced corrosion in sour systems. This paper describes the development of effective inhibitors for corrosion and pitting in the presence of elemental sulfur under sour conditions. This study focuses more on pitting corrosion due to the corrosive characteristics of elemental sulfur than on uniform general corrosion. The general corrosion with the selected inhibitor was highly mitigated and was less than 3.0 mpy while yielding excellent protection against sulfur induced pitting.

Critical Conditions for Initiation of Localized Corrosion of Mild Steels in Contact with Bentonite Used in Geological Disposal Packages of Nuclear Waste

1992 ◽  
Vol 294 ◽  
Author(s):  
Guen Nakayama ◽  
Masatsune Akashi
Keyword(s):  
Mild Steel ◽  
Nuclear Waste ◽  
Localized Corrosion ◽  
Critical Conditions ◽  
Geological Disposal ◽  
Alkaline Environments ◽  
Current Design ◽  
Long Time ◽  
High Level Nuclear Waste ◽  
High Level

ABSTRACTIn the current design of geological disposal of high-level nuclear waste, the use of bentonite to stand as an artificial barrier-cum-buffer between the host rock and the packages made of mild steel is being investigated. Although mild steels commomly have been considered to be passivity in alkaline environments, under certain circumstances, they become liable to localized corrosion, e.g., pitting corrosion and crevice corrosion. Since bentonite can turn the environment alkaline to a pH of approximately 10 when it is mixed with groundwater, critical conditions for the initiation of localized corrosion of mild steel must be known to evaluate the extremely long time integrity of disposal packages serving in such an environment. This paper presents and discusses the observations and results acquired in a series of critical conditions for the initiation of localized corrosion of mild steels in various groundwater-bentonite environments at 20C, with a deaerated aqueous solution of 1 mMol/L [HCO3−] +10 ppm [CI−], simulating the natural groundwater and varying the bentonite content.

Characterization of the Corrosion Behavior of Alloy 22 after Five Years Immersion in Multi-ionic Solutions

2002 ◽  
Vol 757 ◽  
Author(s):  
Lana L. Wong ◽  
David V. Fix ◽  
John C. Estill ◽  
R. Daniel McCright ◽  
Raúl B. Rebak
Keyword(s):  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Electrolyte Solutions ◽  
Underground Water ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Uniform Corrosion ◽  
Waste Container ◽  
Alloy 22

ABSTRACTAlloy 22 (N06022) is the candidate material for the corrosion resistant, outer barrier of the nuclear waste container. Two of the potential corrosion degradation modes of the container are uniform corrosion and localized corrosion. A testing program is under way at the Lawrence Livermore National Laboratory to determine the susceptibility of Alloy 22 to these two forms of corrosion using immersion tests. Metallic coupons are being exposed to several electrolyte solutions simulating concentrated underground water from pH 3 to 10 at 60°C and 90°C. This paper describes the results obtained after more than a five-year exposure of 122 specimens to the testing electrolyte solutions. Results show little general corrosion and the absence of localized corrosion. The maximum general corrosion rate was 23 nm/yr.

The Effect of Alloying Cu on Pitting Corrosion Resistance of Copper-Bearing Ferritic Stainless Steel

2008 ◽  
Vol 569 ◽  
pp. 197-200 ◽  
Author(s):  
Wei Zhang ◽  
De Ning Zou ◽  
Hong Hong Yao ◽  
Jun Yang
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Pitting Corrosion ◽  
Stainless Steels ◽  
Antibacterial Properties ◽  
Ferrite Matrix ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Pitting Corrosion Resistance ◽  
Effect Of Alloying

Copper is a well-known alloying element which is used to improve the resistance to general corrosion of stainless steels. Our previous experiments show that the increase of copper content can acquire the excellent antibacterial properties and can also increase the tendency to cold formability of the ferritic stainless steels. However, the effect of alloying Cu on the resistance to localized corrosion has not been clarified sufficiently. In order to understand the effect of copper on pitting corrosion resistance of the ferritic antibacterial stainless steel, the electrochemical experiments were carried out and the anodic polarization curves were performed in 3.5% NaCl solution for two kinds of steels. The results reveal that the ε-Cu phase in ferrite matrix diminishes pitting corrosion resistance of the antibacterial stainless steel in the chlorides medium. It is connected with the poor passive behavior of the ε-Cu phase inclusions.

scholarly journals Review of Corrosion Modes For Alloy 22 Regarding Lifetime Expectancy of Nuclear Waste Containers

2002 ◽  
Vol 757 ◽  
Author(s):  
Raúl B. Rebak ◽  
John C. Estill
Keyword(s):  
Corrosion Rate ◽  
Nuclear Waste ◽  
Outer Layer ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Corrosion Resistant ◽  
Waste Package ◽  
Environmentally Assisted Cracking ◽  
Alloy 22 ◽  
Lifetime Expectancy

ABSTRACTAlloy 22 (UNS N06022) was selected to fabricate the corrosion resistant outer barrier of a two-layer nuclear waste package container. This paper reviews the main corrosion degradation modes that are predicted for the outer layer of the container. Current results show that the containers would perform well under general corrosion, localized corrosion and environmentally assisted cracking (EAC). For example, the general corrosion rate is expected to be below 100 nm/year and the container is predicted to be outside the range of potential for localized corrosion and environmentally assisted cracking.

scholarly journals Wavelet Transform Modulus Maxima and Holder Exponents Combined with Transient Detection for the Differentiation of Pitting Corrosion Using Electrochemical Noise

CORROSION ◽  
10.5006/2788 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 1001-1010 ◽  
Author(s):  
A.M. Homborg ◽  
P.J. Oonincx ◽  
J.M.C. Mol
Keyword(s):  
Wavelet Transform ◽  
Pitting Corrosion ◽  
Electrochemical Noise ◽  
Localized Corrosion ◽  
General Corrosion ◽  
Hölder Exponent ◽  
Transient Detection ◽  
Time Frequency ◽  
Wavelet Transform Modulus Maxima ◽  
Modulus Maxima

A potentially powerful tool to detect and classify corrosion mechanisms is the analysis of electrochemical noise (EN). Data analysis in the time-frequency domain using, e.g., continuous wavelet transform (CWT) allows the extraction of localized frequency information, providing information on the type of corrosion, i.e., uniform or localized corrosion, from the EN signal. The CWT provides the opportunity to analyze changes in frequency behavior of EN signals over time. In the presence of transients generated by pitting corrosion that occur only during short instants of time, this is an important property. This paper introduces the combination of automated transient detection with wavelet transform modulus maxima (WTMM) and the Holder exponent. WTMM enhances the determination of transient frequencies by indicating the ridges of a CWT spectrum. The Holder exponent, a measure of singularity of an EN signal, provides a single parameter discrimination tool based on WTMM and serves to differentiate between general corrosion and two types of pitting corrosion of stainless steel Type 304 exposed to aqueous HCl solutions of different concentrations and as such at different pH values.

Effects of Chloride, Bromide, and Thiosulfate Ions on the Critical Conditions for Crevice Corrosion of Several Stainless Alloys as a Material for Geological Disposal Packages for Nuclear Waste

1992 ◽  
Vol 294 ◽  
Author(s):  
Guen Nakayama ◽  
Hisao Wakamatsu ◽  
Masatsune Akashi
Keyword(s):  
Stainless Steel ◽  
Nuclear Waste ◽  
Crevice Corrosion ◽  
304 Stainless Steel ◽  
Critical Conditions ◽  
Geological Disposal ◽  
Steel Type ◽  
316 Stainless Steel ◽  
Type 304 ◽  
Type 304 Stainless Steel

ABSTRACTIn addition to mild steel, several stainless alloys are being proposed as materials for packages for geological disposal of high-level nuclear waste. When buried deep underground, the greatest detriment to the integrity of packages made of these alloys is localized corrosion, for which critical conditions for initiation of crevice corrosion in chloride environments, with or without other ions, need be precisely known.Crevice corrosion behavior of Type 304 stainless steel, Type 316 stainless steel, Alloy 825, Ti-Gr.1, and Ti-Gr.12 in solutions containing ions of chloride, bromide (these two for their ordinary presence in natural waters), or thiosulphate (this for the likelihood of microbially influenced corrosion) to varying concentrations have been empirically examined. All of these alloys exhibit much the same concentration dependency of crevice corrosion sensitivity for chloride and bromide ions, while Type 304 stainless steel is particularly sensitive to the thiosulphate ion. The region of insensitivity for chloride ion is wider in the increasing order of Type 304 stainless steel, Type 316 stainless steel, Ti-Gr. 1, and Ti-Gr. 12, with that of Alloy 825 lying somewhere in between.

Localized Corrosion of Stainless Steel in a Nuclear Waste Cooling Water System— Part 1: Crevice Corrosion Studies

CORROSION ◽  
10.5006/0412 ◽  
2012 ◽  
Vol 68 (8) ◽  
pp. 677-687 ◽  
Author(s):  
G.O.H. Whillock ◽  
S.E. Worthington ◽  
C.J. Donohoe
Keyword(s):  
Stainless Steel ◽  
Nuclear Waste ◽  
Crevice Corrosion ◽  
Water System ◽  
Cooling Water ◽  
Chloride Ions ◽  
Localized Corrosion ◽  
Stainless Steel Surface ◽  
Water Radiolysis ◽  
Cooling Water System

Parts of a nuclear waste cooling water system, constructed from an austenitic stainless steel, are known to be susceptible to localized corrosion. This is attributed to the presence of chloride ions in the water, albeit only at low concentrations (<10 mg/L), and oxidants produced by water radiolysis. Experiments were carried out using an engineered crevice connected to a large passive stainless steel surface to demonstrate the viability of crevice corrosion. Similar tests were undertaken to investigate the efficacy of nitrate as an inhibitor. In irradiated water containing up to 300 mg/L Cl− and at temperatures of up to 60°C, crevice corrosion of UNS 30403 and 18Cr-13Ni 1Nb was inhibited by nitrate added at molar ratios of approximately 2.9 to 5.7 with respect to chloride. Once corrosion is inhibited, the nitrate/chloride ratio can be reduced to maintain passivity, but a nitrate:chloride ratio of approximately 0.6 or lower is unlikely to be effective.

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