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Water vapor effects on the corrosion of steel

Description: Critical relative humidity for AISI 1020 carbon steel is 75-85% RH at 65 C. Aggressive electrochemical corrosion occurs above 85% RH, while dry oxidation occurs below 75% RH. The reddish-brown product is probably Fe2O3 or its hydrate; the black oxide layer, Fe3O4. The face surfaces had little or no corrosion, while the mill-machined edges were corroded with nonuniform reddish-brown areas.
Date: November 16, 1995
Creator: Estill, J.C. & Gdowski, G.E.
Partner: UNT Libraries Government Documents Department

The effect of water vapor on the corrosion of carbon steel at 65{degree}C

Description: AISI 1020 carbon steel was exposed to air at various relative humidities at 65{degrees}C. A ``critical relative humidity`` (CRH) of 75--85% was determined. The CRH is the transitional relative humidity where oxidation/corrosion changes from dry oxidation to aqueous film electrochemical corrosion. Short term testing suggests that aqueous film electrochemical corrosion results in the formation of an inner oxide of Fe{sub 3}O{sub 4}, and an outer oxide of a powdery Fe{sub 2}O{sub 3} and/or Fe{sub 2}O{sub 3}{center_dot}xH{sub 2}O.
Date: November 7, 1995
Creator: Gdowski, G.E. & Estill, J.C.
Partner: UNT Libraries Government Documents Department

Corrosion of candidate materials in Lake Rotokawa geothermal exposure

Description: Corrosion rates were determined for CDA 613, CDA 715, A-36 carbon steel, 1020 carbon steel, and Alloy 825 flat coupons which were exposed to geothermal spring water at Paraiki site number 9 near Lake Rotokawa, New Zealand. Qualitative observations of the corrosion performance of Type 304L stainless steel and CDA 102 exposed to the same environment were noted. CDA 715, Alloy 825, 1020 carbon steel, and other alloys are being considered for the materials of construction for high-level radioactive waste containers for the United States civilian radioactive waste disposal program. Alloys CDA 613 and CDA 102 were tested to provide copper-based materials for corrosion performance comparison purposes. A36 was tested to provide a carbon steel baseline material for comparison purposes, and alloy 304L stainless steel was tested to provide an austenitic stainless steel baseline material for comparison purposes. In an effort to gather corrosion data from an environment that is rooted in natural sources of water and rock, samples of some of the proposed container materials were exposed to a geothermal spring environment. At the proposed site at Yucca Mountain, Nevada, currently under consideration for high-level nuclear waste disposal, transient groundwater may come in contact with waste containers over the course of a 10,000-year disposal period. The geothermal springs environment, while extremely more aggressive than the anticipated general environment at Yucca Mountain, Nevada, could have similarities to the environment that arises at selected local sites on a container as a result of crevice corrosion, pitting corrosion, microbiologically influenced corrosion (MIC), or the concentration of the ionic species due to repetitive evaporation or boiling of the groundwater near the containers. The corrosion rates were based on weight loss data obtained after six weeks exposure in a 90{degrees}C, low-pH spring with relatively high concentrations of SO{sub 4}{sup 2-} and Cl{sup -}.
Date: May 1, 1995
Creator: Estill, J.C. & McCright, R.D.
Partner: UNT Libraries Government Documents Department

Corrosion Rate of Alloy 22 as a Function of Immersion Time

Description: Alloy 22 (N06022) is a nickel (Ni) based alloy containing nominally 22% Chromium (Cr), 13% Molybdenum (Mo) and 3% tungsten (W). Alloy 22 is highly resistant to general and localized corrosion such as pitting corrosion and stress corrosion cracking. Due to the formation of a stable passive film, when Alloy 22 is immersed in certain electrolytes, its corrosion potential (E{sub corr}) increases and its corrosion rate (CR) decreases as a function of the immersion time. This paper discusses the evolution of E{sub corr} and corrosion rate (CR) of creviced Alloy 22 specimens in six different mixtures of sodium chloride (NaCl) and potassium nitrate (KNO{sub 3}) at 100 C. Two types of specimens were used, polished as-welded (ASW) and as-welded solution plus heat-treated (ASW+SHT). The latter contained the black annealing oxide film on the surface. Results show that, for the two type of materials, as the immersion time increases, E{sub corr} increased and the CR decreased. Even for concentrated brine solutions at 100 C the CR was < 50 nm/year after more than 100 days immersion.
Date: March 21, 2005
Creator: Estill, J C; Hust, G A; King, K J & Rebak, R B
Partner: UNT Libraries Government Documents Department

Electronic weight- and dimensional-data entry in a computer database

Description: The purpose of this technical implementing procedure (TIP) is to describe the procedure used to obtain dimensional and weight information for test specimens and enter that data into an electronic database. This TIP applies to Activity E-20-50, ''Long-Term Corrosion Studies'', and it pertains to weighing and measuring of specimens, and the storage of that data in an electronic database. Data is stored in the electronic database ''Microsoft Access''. Data is entered by electronic data transfer from a digital caliper (Fowler Ultra-Cal Mark III) and an electronic analytical balance (Mettler AT200).
Date: July 2, 1996
Creator: Estill, J.
Partner: UNT Libraries Government Documents Department

User-calibration of Fowler Ultra-Cal Mark III Digital caliper

Description: The purpose of this technical implementing procedure (TIP) is to describe the procedure that will be employed for user-calibration of a digital caliper used in the determination of specimen dimensions. A caliper is used for some of the activities of the Scientific Investigation Plan (SIP) Metal Barrier Selection and Testing (SIP-CM-01, WBS {number_sign} 1.2.2.5.1). In particular, it will be used for Activity E-20-50, Long-Term Corrosion Studies. This procedure describes the methodology for user calibration of a Fowler Ultra-Cal Mark III digital caliper. National Institutes of Standards and Technology (NIST) traceable gauge blocks are employed in the calibration procedure.
Date: September 19, 1996
Creator: Estill, J.
Partner: UNT Libraries Government Documents Department

User-calibration of Mettler AT200 analytical balance

Description: The purpose of this technical implementing procedure (TIP) is to describe the calibration of the Mettler AT200 analytical balance or similar type balance (henceforth called the balance). This balance is used for activities of the Scientific Investigation Plan (SIP) ''Metal Barrier Selection and Testing'' (SIP-CM-01, WBS {number_sign} 1.2.2.5.1). In particular, it will be used for Activity E-20-50, ''Long-Term Corrosion Studies.'' The balance will be used for weighing test specimens and reagent chemicals. However, it is not limited to these uses. The calibration procedures consist of activating the internal (self) calibration of the apparatus, and weighing and recording of traceable standards. The balance is equipped with self (internal) calibration and linearization capabilities. It has an internal (built in) set of weights which are used for self calibration. The standard weights are traceable to National Institute of Standards and Technology (NIST).
Date: July 2, 1996
Creator: Estill, J.
Partner: UNT Libraries Government Documents Department

Comparison of Electrochemical Methods to Determine Crevice Corrosion Repassivation Potential of Alloy 22 in Chloride Solutions

Description: Alloy 22 (N06022) is a nickel-based alloy highly resistant to corrosion. In some aggressive conditions of high chloride concentration, temperature and applied potential, Alloy 22 may suffer crevice corrosion, a form of localized corrosion. There are several electrochemical methods that can be used to determine localized corrosion in metallic alloys. One of the most popular for rapid screening is the cyclic potentiodynamic polarization (CPP). This work compares the repassivation potentials obtained using CPP to related repassivation potential values obtained using the Tsujikawa-Hisamatsu Electrochemical (THE) method and the potentiostatic (POT) method. Studied variables included temperature and chloride concentration. The temperature was varied from 30 C and 120 C and the chloride concentration was varied between 0.0005 M to 4 M. Results show that similar repassivation potentials were obtained for Alloy 22 using CPP and THE methods. Generally, under more aggressive conditions, the repassivation potentials were more conservative using the CPP method. POT tests confirmed the validity of the repassivation potential as a threshold below which localized corrosion does not nucleate. The mode of attack in the tested specimens varied depending if the test method was CPP or THE; however, the repassivation potential remained the same.
Date: August 23, 2004
Creator: Evans, K.; Yilmaz, A.; Day, S.; Wong, L. & Estill, J.
Partner: UNT Libraries Government Documents Department

General and Localized corrosion of Austenitic and Borated Stainless Steels in Simulated Concentrated Ground Waters

Description: Boron containing stainless steels are used in the nuclear industry for applications such as spent fuel storage, control rods and shielding. It was of interest to compare the corrosion resistance of three borated stainless steels with standard austenitic alloy materials such as type 304 and 316 stainless steels. Tests were conducted in three simulated concentrated ground waters at 90 C. Results show that the borated stainless were less resistant to corrosion than the witness austenitic materials. An acidic concentrated ground water was more aggressive than an alkaline concentrated ground water.
Date: May 28, 2004
Creator: Fix, D.; Estill, J.; Wong, L. & Rebak, R.
Partner: UNT Libraries Government Documents Department

Stress Corrosion Cracking Behavior of Alloy 22 in Multi-Ionic Aqueous Environments

Description: The US Department of Energy is characterizing a potential repository site for nuclear waste in Yucca Mountain (NV). In its current design, the nuclear waste containers consist of a double metallic layer. The external layer would be made of NO6022 or Alloy 22 (Ni-22Cr-13Mo-3W-3Fe). Since over their lifetime, the containers may be exposed to multi-ionic aqueous environments, a potential degradation mode of the outer layer could be environmentally assisted cracking (EAC) or stress corrosion cracking (SCC). In general, Alloy 22 is extremely resistant to SCC, especially in concentrated chloride solutions. Current results obtained through slow strain rate testing (SSRT) shows that Alloy 22 may suffer SCC in simulated concentrated water (SCW) at applied potentials approximately 400 mV more anodic than the corrosion potential (E{sub rr}).
Date: July 15, 2002
Creator: King, K.J.; Estill, J.C. & Rebak, R.B.
Partner: UNT Libraries Government Documents Department

Long-Term Corrosion Behavior of Alloy 22 in 5M CaCl2 at 120 C

Description: In conditions where tight crevices exist in hot chloride containing solutions Alloy 22 may suffer crevice corrosion. The occurrence (or not) of crevice corrosion in a given environment (e.g, salt concentration and temperature), is governed by the values of the critical potential (E{sub crit}) for crevice corrosion and the corrosion potential (E{sub corr}). This paper discusses the evolution of E{sub corr} and corrosion rate (CR) of creviced Alloy 22 specimens in 5 M calcium chloride (CaCl{sub 2}) at 120 C. Tested specimens included non-creviced rods and multiple creviced assemblies (MCA) both non-welded (wrought) and welded. Results show that Alloy 22 suffers crevice corrosion under the open circuit conditions in the aerated hot CaCl{sub 2} brine. However, after more than a year of immersion the propagation of crevice corrosion was not significant. The general corrosion rate decreased or remained unchanged as the immersion time increased. For rods and MCA specimens, the corrosion rate was lower than 100 nm/year after more than a year immersion time.
Date: May 8, 2006
Creator: Estill, J.C.; Hust, G.A.; Evans, K.J.; Stuart, M.L. & Rebak, R.B.
Partner: UNT Libraries Government Documents Department

Long-Term Corrosion Behavior of Alloy 22 in 5 M CaCl2 at 120?C

Description: In conditions where tight crevices exist in hot chloride containing solutions Alloy 22 may suffer crevice corrosion. The occurrence (or not) of crevice corrosion in a given environment (e.g. salt concentration and temperature), is governed by the values of the critical potential (E{sub crit}) for crevice corrosion and the corrosion potential (E{sub corr}). This paper discusses the evolution of E{sub corr} and corrosion rate (CR) of creviced Alloy 22 specimens in 5 M calcium chloride (CaCl{sub 2}) at 120 C. Tested specimens included non-creviced rods and multiple creviced assemblies (MCA) both non-welded (wrought) and welded. Results show that Alloy 22 suffers crevice corrosion under the open circuit conditions in the aerated hot CaCl{sub 2} brine. However, after more than a year immersion the propagation of crevice corrosion was not significant. The general corrosion rate decreased or remained unchanged as the immersion time increased. For rods and MCA specimens, the corrosion rate was lower than 100 nm/year after more than a year immersion time.
Date: February 5, 2006
Creator: Estill, J C; Hust, G A; Evans, K J; Stuart, M L & Rebak, R B
Partner: UNT Libraries Government Documents Department

Integrated Corrosion Facility for long-term testing of candidate materials for high-level radioactive waste containment

Description: A long-term-testing facility, the Integrated Corrosion Facility (I.C.F.), is being developed to investigate the corrosion behavior of candidate construction materials for high-level-radioactive waste packages for the potential repository at Yucca Mountain, Nevada. Corrosion phenomena will be characterized in environments considered possible under various scenarios of water contact with the waste packages. The testing of the materials will be conducted both in the liquid and high humidity vapor phases at 60 and 90{degrees}C. Three classes of materials with different degrees of corrosion resistance will be investigated in order to encompass the various design configurations of waste packages. The facility is expected to be in operation for a minimum of five years, and operation could be extended to longer times if warranted. A sufficient number of specimens will be emplaced in the test environments so that some can be removed and characterized periodically. The corrosion phenomena to be characterized are general, localized, galvanic, and stress corrosion cracking. The long-term data obtained from this study will be used in corrosion mechanism modeling, performance assessment, and waste package design. Three classes of materials are under consideration. The corrosion resistant materials are high-nickel alloys and titanium alloys; the corrosion allowance materials are low-alloy and carbon steels; and the intermediate corrosion resistant materials are copper-nickel alloys.
Date: October 1, 1994
Creator: Estill, J.C.; Dalder, E.N.C.; Gdowski, G.E. & McCright, R.D.
Partner: UNT Libraries Government Documents Department

Stress corrosion cracking of Ni-base and Ti alloys under controlled potential

Description: Susceptibility to stress corrosion cracking (SCC) of alloy C-22 and Ti Gr-12, two candidate alloys for the inner-container of the multi-barrier nuclear waste package, was evaluated by using the slow-strain-rate (SSR) test technique in a deaerated acidic brine (pH {approx} 2.70) at 90 C. The strain rate used was 3.3 x 10{sup {minus}6} sec{sup {minus}1}. Prior to being tested in the acidic brine, specimens of each alloy were pulled inside the test chamber in the dry condition at room temperature (RT). Then specimens were exposed to the test solution while being strained under different controlled electrochemical potentials. The magnitude of the controlled potential was selected based on the corrosion potential measured in the test solution prior to straining of the specimen. Results indicate that, for Ti Gr-12, the times to failure were significantly shorter compared to those for alloy C-22. Furthermore, Ti Gr-12 showed reduced ductility in terms of percent reduction in area and true fracture stress, as the controlled potential became more cathodic. Results also indicate that the time-to-failure and percent elongation reached the minimum values when Ti Gr-12 was tested under impressed potential of {minus}1162 mV. Finally, metallographic examination was performed to evaluate the primary fracture, and the secondary cracking, if any, along the gage section of the broken tensile specimen.
Date: October 22, 1998
Creator: Estill, J C; Gordon, S R; Logeteta, L F & Roy, A K
Partner: UNT Libraries Government Documents Department

Development of integrated mechanistically-based degradation-mode models for performance assessment of high-level waste containers

Description: Alloy 22 [UNS NO60221] is now being considered for construction of high level waste containers to be emplaced at Yucca Mountain and elsewhere. In essence, this alloy is 20.0-22.5% Cr, 12.5-14.5% MO, 2.0-6.0% Fe, 2.5-3.5% W, with the balance being Ni. Other impurity elements include P, Si, S, Mn, Co and V. Cobalt may be present at a maximum concentration of 2.5%. Detailed mechanistic models have been developed to account for the corrosion of Alloy 22 surfaces in crevices that will inevitably form. Such occluded areas experience substantial decreases in pH, with corresponding elevations in chloride concentration. Experimental work has been undertaken to validate the crevice corrosion model, including parallel studies with 304 stainless steel.
Date: December 21, 1998
Creator: Estill, J C; Farmer, J C; Gordon, S R & McCright, R D
Partner: UNT Libraries Government Documents Department

General and localized corrosion of the drip shield

Description: Ti Gr 7 is an extremely corrosion resistant material, with a very stable passive film. Based upon exposures in the LTCTF, it has been determined that the general corrosion and oxidation rates of Ti Gr 7 are essentially below the level of detection. In any event, over the 10,000 year life of the repository, general corrosion and oxidation should not be life limiting. The large separation between measured corrosion and threshold potentials indicate that localized breakdown of the passive film is unlikely under plausible conditions, even in SSW at 120 C. In the future, the pH and current in crevices formed from Ti Gr 7 should be determined experimentally. With exposures of two years, no significant evidence of crevice corrosion has been observed with Ti Gr 16 in SDW, SCW, and SAW at temperatures up to 9O C, though many of the samples have a beautiful green patina. An abstracted model has been presented, with parameters determined experimentally, that should enable performance assessment to account for the general and localized corrosion of this material. A feature of this model is the use of the materials specification to limit the range of corrosion and threshold potentials, thereby making sure that substandard materials prone to localized attack are avoided.
Date: August 20, 1999
Creator: Estill, J C; Farmer, J C; McCright & D, R
Partner: UNT Libraries Government Documents Department

Development of integrated mechanistically-based degradation-mode models for performance assessment of high-level waste containers

Description: Alloy 22 [UNS NO60221] is now being considered for construction of high level waste containers to be emplaced at Yucca Mountain and elsewhere. In essence, this alloy is 21% Cr, 13% MO, 4% Fe, 3% W, 2% Co, with the balance being Ni. Variants without tungsten are also being considered. Detailed mechanistic models have been developed to account for the corrosion of Alloy 22 surfaces in crevices that will inevitably form. Such occluded areas experience substantial decreases in pH, with corresponding elevations in chloride concentration. Experimental work has been undertaken to validate the crevice corrosion model, including parallel studies with 304 stainless steel.
Date: November 2, 1998
Creator: Farmer, J C; McCright, R D; Estill, J C & Gordon, S R
Partner: UNT Libraries Government Documents Department

Distribution of soluble and precipitated iron and chromium products generated by anodic dissolution of 316L stainless steel and alloy C-22: final report

Description: At near neutral pH and at applied potentials above the threshold potential for localized breakdown of the passive film, virtually all of the dissolved chromium appeared to be in the hexavalent oxidation state (Cr(VI)). In acidic environments, such as crevice solutions formed during the crevice corrosion of 316L and C-22 samples in 4 M NaCl, virtually all of the dissolved chromium appeared to be in the trivalent oxidation state (Cr(III)). These general observations appear to be consistent with the Pourbaix diagram for chromium (Pourbaix 1974), pp. 307-321. At high pH and high anodic polarization (pH {approximately} 8 and 800 mV vs. SHE), the predominate species is believed to be the soluble chromate anion (CrO{sub 4}{sup 2{minus}}). At the same pH, but lower polarization (pH {approximately} 8 and 0 mV vs. SHE), the predominate species are believed to be precipitates such as trivalent Cr(OH){sub 3} {center_dot} n(H{sub 2}O) and hexavalent Cr{sub 2}O{sub 3}. In acidified environments such as those found in crevices (pH < 3), soluble Cr{sup 3+} is expected to form over a wide range of potential extending from 400 mV vs. SHE to approximately 1200 mV vs. SHE. Again, this is consistent with the observations from the creviced samples. In earlier studies by the principal investigator, it has been found that low-level chromium contamination in ground water is usually in the hexavalent oxidation state (Farmer et al. 1996). In general, dissolved iron measured during the crevice experiments appears to be Fe(II) in acidic media and Fe(III) in near-neutral and alkaline solutions (table 3). In the case of cyclic polarization measurements, the dissolved iron measured at the end of some cyclic polarization measurements with C-22 appeared to be in the Fe(III) state. This is probably due to the high electrochemical potential at which these species were generated during the potential ...
Date: August 11, 1999
Creator: Estill, J; Farmer, J; Gordon, S; King, K; Logotetta, L & Silberman, D
Partner: UNT Libraries Government Documents Department

Studies of Corrosion Resistant Materials Being Considered for High-Level Nuclear Waste Containment in Yucca Mountain Relevant Environments

Description: Containment of spent nuclear fuel and vitrified forms of high level nuclear waste require use of materials that are highly corrosion resistant to all of the anticipated environmental scenarios that can occur in a geological repository. Ni-Cr-Mo Alloy 22 (UNS N60622) is proposed for the corrosion resistant outer barrier of a two-layer waste package container at the potential repository site at Yucca Mountain. A range of water compositions that may contact the outer barrier is under consideration, and a testing program is underway to characterize the forms of corrosion and to quantify the corrosion rates. Results from the testing support models for long term prediction of the performance of the container. Results obtained to date indicate a very low general corrosion rate for Alloy 22 and very high resistance to all forms of localized and environmentally assisted cracking in environments tested to date.
Date: December 9, 2001
Creator: McCright, R.D.; Ilevbare, G.; Estill, J. & Rebak, R.
Partner: UNT Libraries Government Documents Department

Anodic Behavior of Alloy 22 in High Nitrate Brines at Temperatures Higher than 100(degree)C

Description: Alloy 22 (N06022) may be susceptible to crevice corrosion in chloride solutions. Nitrate acts as an inhibitor to crevice corrosion. Several papers have been published regarding the effect of nitrate on the corrosion resistance of Alloy 22 at temperatures 100 C and lower. However, very little is known about the behavior of this alloy in highly concentrated brines at temperatures above 100 C. In the current work, electrochemical tests have been carried out to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 160 C at ambient atmospheres. Even though Alloy 22 may adopt corrosion potentials in the order of +0.5 V (in the saturated silver chloride scale), it does not suffer crevice corrosion if there is high nitrate in the solution. That is, the inhibitive effect of nitrate on crevice corrosion is active for temperatures higher than 100 C.
Date: March 28, 2006
Creator: Ilevbare, G O; Etien, R A; Estill, J C; Hust, G A; Yilmaz, A; Stuart, M L et al.
Partner: UNT Libraries Government Documents Department

ANODIC BEHAVIOR OF ALLOY 22 IN HIGH NITRATE BRINES AT TEMPERATURES HIGHER THAN 100C

Description: Alloy 22 (N06022) may be susceptible to crevice corrosion in chloride solutions. Nitrate acts as an inhibitor to crevice corrosion. Several papers have been published regarding the effect of nitrate on the corrosion resistance of Alloy 22 at temperatures 100 C and lower. However, very little is known about the behavior of this alloy in highly concentrated brines at temperatures above 100 C. In the current work, electrochemical tests have been carried out to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 160 C at ambient atmospheres. Even though Alloy 22 may adopt corrosion potentials in the order of +0.5 V (in the saturated silver chloride scale), it does not suffer crevice corrosion if there is high nitrate in the solution. That is, the inhibitive effect of nitrate on crevice corrosion is active for temperatures higher than 100 C.
Date: April 20, 2006
Creator: LLEVBARE, G.O.; ESTILL, J.C.; YILMAZ, A.; ETIEN, R.A. & STUART, G.A. HUST M.L.
Partner: UNT Libraries Government Documents Department

Long Term Corrosion Potential and Corrosion Rate of Creviced Alloy 22 in Chloride Plus Nitrate Brines

Description: Alloy 22 is a nickel base alloy highly resistant to all forms of corrosion. In conditions where tight crevices exist in hot chloride containing solutions and at anodic potentials, Alloy 22 may suffer crevice corrosion, a form of localized attack. The occurrence (or not) of crevice corrosion in a given environment (e.g. salt concentration and temperature), is governed by the values of the critical potential (E{sub crit}) for crevice corrosion and the corrosion potential (E{sub corr}) that the alloy may establish in the studied environment. If E{sub corr} is equal or higher than E{sub crit}, crevice corrosion may be expected. In addition, it is generally accepted that as Alloy 22 becomes passive in a certain environment, its E{sub corr} increases and its corrosion rate (CR) decreases. This paper discusses the evolution of E{sub corr} and corrosion rate (CR) of creviced Alloy 22 specimens in six different mixtures of sodium chloride (NaCl) and potassium nitrate (KNO{sub 3}) at 100 C. The effect of immersion time on the value of E{sub crit} was also determined. Two types of specimens were used, polished as-welded (ASW) and as-welded plus solution heat-treated (ASW+SHT). The latter contained the black annealing oxide film on the surface. Results show that, as the immersion time increases, E{sub corr} increased and the CR decreased. Even for highly concentrated brine solutions at 100 C the CR was < 30 nm/year after more than 250 days immersion. Some of the exposed specimens (mainly the SHT specimens) suffered crevice corrosion at the open circuit potential in the naturally aerated brines. Immersion times of over 250 days did not reduce the resistance of Alloy 22 to localized corrosion.
Date: November 5, 2005
Creator: Evans, K J; Stuart, M L; Etien, R A; Hust, G A; Estill, J C & Rebak, R B
Partner: UNT Libraries Government Documents Department

Passive Corrosion Behavior of Alloy 22 in Multi-Ionic Aqueous Environments

Description: In current waste packaging design, Alloy 22 (Ni-22Cr-13Mo-3W-3Fe) has been chosen as the candidate materials to fabricate a 2 cm outer layer of the high-level nuclear waste containers, as part of proposed geological repository at Yucca Mountain, Nevada. During the repository period, the container materials will be subject to the corrosion due to its exposure to the multi-ionic aqueous environments. Although Alloy 22 has demonstrated excellent corrosion resistance, but accumulation of small yearly corrosion rate for 10,000 or more years can be significant enough. The goal of this research is to seek alternative techniques to obtain a reasonably confident corrosion rate determination, since the conventional weight loss technique requires many years to achieve a detectable weight loss in Alloy 22 samples. This paper will discuss the latest experiment results in using potentiostatic technique to determine passive dissolution rates.
Date: June 3, 2002
Creator: Lian, T.; Estill, J.C.; Hust, G.A.; Fix, D.V. & Rebak, R.B.
Partner: UNT Libraries Government Documents Department

Passive films and blistering of titanium

Description: Coupons of titanium alloys under consideration as components of the Engineered Barrier System in the proposed repository at Yucca Mountain have been evaluated for their passive film composition and stability. Oxide depths and compositions on specimens exposed in long-term corrosion testing for one year were determined with x-ray photoemission spectroscopy. The specimens removed from long-term testing, as well as separate coupons polarized cathodically in an electrochemical cell, exhibited blistering associated with hydride formation in both scanning electron microscopy and atomic force microscopy.
Date: December 1, 1998
Creator: Bedrossian, P J; Estill, J C; Farmer, J C; McCright, R D & Phinney, D L
Partner: UNT Libraries Government Documents Department