160 Matching Results

Search Results

Advanced search parameters have been applied.

The Effect of Temperature on the Breakdown and Repassivation Potentials of Welded Alloy 22 In 5 M CACI2

Description: The study of the electrochemical behavior of wrought and welded Alloy 22 was carried out in 5 M CaCl{sub 2} as a function of temperatures between 45 and 120 C with Multiple Crevice Assembly (MCA) specimens. The susceptibility to corrosion was found to increase with increase in electrolyte temperature in both the wrought (in the mill annealed condition) and the welded forms of the alloy. The weld metal was found to be less susceptible to localized corrosion under the conditions tested.
Date: July 5, 2006
Creator: IIevbare, G.O.
Partner: UNT Libraries Government Documents Department

O2 Electroreduction on Ni-Cr-Mo Alloys

Description: Oxygen (O{sub 2}) reduction is the most likely process for sustaining metal oxidation in air through electrochemical ''local cells'' on the metal surface. O{sub 2} reduction occurring at one surface site is the sink for electrons generated during metal oxidation at another. Metal corrosion is reduced when O{sub 2} reduction is slowed or arrested; a process that leads to ''cathodic stifling'', O{sub 2} reduction sites become alkaline through the generation of hydroxide. The O{sub 2} reduction of two Ni-Cr-Mo alloys, i.e. C22 and C276 alloys, was studied in a half-cell with aqueous KOH electrolyte to learn the behavior of the O{sub 2} reduction local cells on the passive metal surface. This is to give experimental inputs to computational methods for predicting alloy corrosion. Fresh and aged alloy metal surfaces were studied in alkaline aqueous media with and without nitrate (1M KNO{sub 3}) in the presence and absence of O{sub 2}-Alloy behavior was characterized by electrochemical impedance spectroscopy (EIS) and voltammetry with a still electrode and a rotating ring-disk electrode (RRDE). A spectroscopic graphite rod was the auxiliary electrode, and Saturated Calomel (SCE) was the reference electrode.
Date: June 9, 2006
Creator: Rogers, S.P.; Gervasio, D.F. & Payer, J.H.
Partner: UNT Libraries Government Documents Department

Examination of Corrosion Products and the Alloy Surface After Crevice Corrosion of a Ni-Cr-Mo- Alloy

Description: The objective of this study is to investigate the composition of corrosion products and the metal surface within a crevice after localized corrosion. The analysis provides insight into the propagation, stifling and arrest processes for crevice corrosion and is part of a program to analyze the evolution of localized corrosion damage over long periods of time, i.e. 10,000 years and longer. The approach is to force the initiation of crevice corrosion by applying anodic polarization to a multiple crevice assembly (MCA). Results are reported here for alloy C-22, a Ni-Cr-Mo alloy, exposed to a high temperature, concentrated chloride solution. Controlled crevice corrosion tests were performed on C-22 under highly aggressive, accelerated condition, i.e. 4M NaCl, 100 C and anodic polarization to -0.15V-SCE. The crevice contacts were by either a polymer tape (PTFE) compressed by a ceramic former or by a polymer (PTFE) crevice former. Figure 1 shows the polarization current during a crevice corrosion test. After an incubation period, several initiation-stifle-arrest events were indicated. The low current at the end of the test indicated that the metal surface had repassivated.
Date: June 9, 2006
Creator: Shan, X. & Payer, J.H.
Partner: UNT Libraries Government Documents Department

The Electrochemical Behavior of Alloy in Extreme Chloride and Bitrate Environments

Description: Alloy 22 specimens were tested in high temperature (100 to 160 C), high concentration chloride and nitrate environments. Results of this study indicate that increasing nitrate to chloride ratio to 0.5 in these electrolytes increases resistance to localized breakdown and enhances repassivation. In these extreme environments, localized corrosion occurred by pitting even though specimens were tested using artificial crevice formers. Open circuit (E{sub corr}), breakdown and repassivation potentials all increase, and pitting morphology changes as nitrate to chloride ratio increases from 0.05 and 0.15 to 0.5. Results also indicate that increasing the temperature from 100 to 160 C increases E{sub corr} values, while breakdown potentials and repassivation potentials peak at 130 C for the 0.5 nitrate to chloride ratio electrolytes.
Date: July 27, 2006
Creator: Etien, R.A.; Gordon, S.R. & Ilevbare, G.O.
Partner: UNT Libraries Government Documents Department

Comparison of Ceramic, Metal and Polymer Crevice Formers on the Crevice Corrosopn Behavior of Ni-CR-Mo Alloy C22

Description: A necessary condition for crevice corrosion is that a crevice former create a sufficiently tight, restricted geometry on the metal surface to support the development of critical crevice chemistry. Crevice corrosion is affected by the crevice geometry (tightness) and the properties of the crevice former. The objective of this study is to determine the effect of the crevice former material on the evolution of localized corrosion-damage. A standard crevice corrosion test method is modified by (a) the use of ceramic, metal or polymer materials as the crevice former and (b) the variation of size and shape of the crevice. This study focuses on the post initiation stage of crevice corrosion and addresses factors that may limit the initiation of localized corrosion and also slow or stop the continued propagation of corrosion. Controlled crevice corrosion tests are performed under aggressive, accelerated conditions on Ni-Cr-Mo alloy C-22 and other alloys for comparison. Multiple techniques are used to examine the crevice corrosion damage evolution. Current measurements during the test provide a direct measure of the corrosion rate and indicate the initiation and any stifling or arrest. The localized corrosion is found to be stifled or arrested under several test conditions. The corrosion damage volume and profile are quantitatively measured with optical and SEM 3D reconstruction methods. Analysis by SEMIEDS, XPS and AES show that the corrosion products within the damaged crevice area are enriched in W, Mo, 0 , while being depleted in Cr, Ni, Fe. The results on C-22, SS3 16 and other alloys show that a PTFE tape covered ceramic was the most active crevice former, solid polymer crevice formers (PTFE or Kel-F) are less active, while no distinguishable crevice corrosion was observed with a ceramic material only as the crevice former in direct contact with the metal. The affects are ...
Date: May 8, 2006
Creator: Shan, X. & Payer, J.H.
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

Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.

Description: Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.
Date: August 12, 2002
Creator: Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E. et al.
Partner: UNT Libraries Government Documents Department

Effect of Temperature and Electrolyte Composition on the Susceptibility of Alloy 22 to Localized Corrosion

Description: The study of the electrochemical behavior of Alloy 22 has been carried out in various concentrated environments using different sample configurations. Comparisons were made between the electrochemical behaviors of Alloy 22 in concentrated chloride solutions, and in concentrated chloride solutions with nitrate ions (NO{sub 3}{sup -}). In other experiments, the effect of fluoride ions (F{sup -}) was investigated. These comparative studies were performed at various temperatures. The rate of corrosion was found to increase with increase in temperature. The presence of nitrate ions reduced corrosion attack on Alloy 22. F{sup -} was found to be more benign to Alloy 22 compared with chloride ions (Cl{sup -}). However a combination of F{sup -} and Cl{sup -} was found to initiate deeper crevices compared with the only Cl{sup -} in the electrolyte.
Date: October 7, 2002
Creator: Day, S.D.; Evans, K.J. & Ilevbare, G.O.
Partner: UNT Libraries Government Documents Department

STIFLING OF CREVICE CORROSION IN ALLOY 22

Description: Artificially creviced Alloy 22 (N06022) specimens may be susceptible to crevice corrosion in presence of hot chloride containing solutions. The presence of oxyanions in the electrolyte, especially nitrate, may inhibit the nucleation and growth of crevice corrosion. Constant potential tests were performed using tightly creviced specimens of Alloy 22. It was found that crevice corrosion may initiate when a constant potential above the crevice repassivation potential is applied. It was found that as the crevice corrosion nucleated, the current initially increased but later decreased. The net measured current can be converted into penetration following a power law fit of the experimental data. The average power law coefficient ''n'' was found to be 0.439, suggesting that even under constant applied potential, crevice corrosion penetration is diffusion controlled.
Date: July 1, 2005
Creator: Mon, K.G.; Gordon, G.M. & Rebak, R.B.
Partner: UNT Libraries Government Documents Department

Determination of the Crevice Repassivation Potential of Alloy 22 By a Potentiodynamic-Galvanostatic-Potentiostatic Method

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 results obtained by measuring the localized corrosion resistance of Alloy 22 using both CPP and the more cumbersome Tsujikawa-Hisamatsu Electrochemical (THE) method. The electrolytes used were 1 M NaCl and 5 M CaCl{sub 2}, both at 90 C. Results show that similar repassivation potentials were obtained for Alloy 22 using both methods. That is, in cases where localized corrosion is observed using the fast CPP method, there is no need to use THE method since it takes ten times longer to obtain comparable results in spite of the mode of corrosion attack is different in the tested specimens.
Date: June 2004
Creator: Evans, K.; Wong, L. & Rebak, R.
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

Effect of Nitrate on the Repassivation Potential of Alloy 22 in Chloride Containing Environment

Description: The study of Alloy 22 was undertaken in several selected nitrate/chloride (NO{sub 3}{sup -}/Cl{sup -}) electrolytes with chloride concentrations [Cl{sup -}] of 1.0, 3.5 and 6.0 molal with [NO{sub 3}{sup -}]/[Cl{sup -}] ratios of 0.05, 0.15 and 0.5 at temperatures up to 100 C. The repassivation potentials increased with increase in [NO{sub 3}{sup -}]/[Cl{sup -}] ratio and decreased with increase in temperature. The absolute [Cl{sup -}] was found to have less of an effect on the repassivation potential compared with temperature and the [NO{sub 3}{sup -}]/[Cl{sup -}]. Regression analyses were carried out to describe the relationship between the repassivation potential, temperature, [Cl{sup -}] and [NO{sub 3}{sup -}] for the conditions tested.
Date: September 21, 2004
Creator: Ilevbare, G.; King, K.; Gordon, S.; Elayat, H.; Gdowski, G. & Summers, T.
Partner: UNT Libraries Government Documents Department

Stress Corrosion Cracking of Annealed and Cold Worked Titanium Grade 7 and Alloy 22 in 110 C Concentrated Salt Environments

Description: Stress corrosion crack growth studies have been performed on annealed and cold worked Titanium Grade 7 and Alloy 22 in 110 C, aerated, concentrated, high pH salt environments characteristic of concentrated ground water. Following a very careful transition from fatigue precracking conditions to SCC conditions, the long term behavior under very stable conditions was monitored using reversing dc potential drop. Titanium Grade 7 exhibited continuous crack growth under both near-static and complete static loading conditions. Alloy 22 exhibited similar growth rates, but was less prone to maintain stable crack growth as conditions approached fully static loading.
Date: November 8, 2000
Creator: Andresen, P.
Partner: UNT Libraries Government Documents Department

EFFECT OF CHEMISTRY VARIATIONS IN PLATE AND WELD FILLER METAL ON THE CORROSION PERFORMANCE OF NI-CR-MO ALLOYS

Description: The ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022) and Alloy 686 (N06686). The compositions of each element are given in a range. For example, the content of Mo is specified from 12.5 to 14.5 weight percent for Alloy 22 and from 15.0 to 17.0 weight percent for Alloy 686. It was important to determine how the corrosion rate of welded plates of Alloy 22 using Alloy 686 weld filler metal would change if heats of these alloys were prepared using several variations in the composition of the elements even though still in the range specified in B 575. All the material used in this report were especially prepared at Allegheny Ludlum Co. Seven heats of plate were welded with seven heats of wire. Immersion corrosion tests were conducted in a boiling solution of sulfuric acid plus ferric sulfate (ASTM G 28 A) using both as-welded (ASW) coupons and solution heat-treated (SHT) coupons. Results show that the corrosion rate was not affected by the chemistry of the materials in the range of the standards.
Date: February 7, 2006
Creator: Fix, D.V.
Partner: UNT Libraries Government Documents Department

PFBC hot gas cleanup test program. Quartery report, April--June 1995

Description: This is the twenty-third Technical Progress Report submitted to the Department of Energy (DOE) in connection with the cooperative agreement between the DOE and Ohio Power Company for the Tidd PFBC Hot Gas Clean Up Test Facility. This report covers the work completed during the Second Quarter of CY 1995. During this quarter, the Tidd APF was opened and the internals removed for inspection. Final equipment inspections were also performed. A draft of the final report for the program was nearing completion at the end of the quarter.
Date: July 1, 1995
Partner: UNT Libraries Government Documents Department

Materials performance in a high-level radioactive waste vitrification system

Description: The Defense Waste Processing Facility (DWPF) is a Department of Energy Facility designed to vitrify highly radioactive waste. An extensive materials evaluation program has been completed on key components in the DWPF after twelve months of operation using nonradioactive simulated wastes. Results of the visual inspections of the feed preparation system indicate that the system components, which were fabricated from Hastelloy C-276, should achieve their design lives. Significant erosion was observed on agitator blades that process glass frit slurries; however, design modifications should mitigate the erosion. Visual inspections of the DWPF melter top head and off gas components, which were fabricated from Inconel 690, indicated that varying degrees of degradation occurred. Most of the components will perform satisfactorily for their two year design life. The components that suffered significant attack were the borescopes, primary film cooler brush, and feed tubes. Changes in the operation of the film cooler brush and design modifications to the feed tubes and borescopes is expected to extend their service lives to two years. A program to investigate new high temperature engineered materials and alloys with improved oxidation and high temperature corrosion resistance will be initiated.
Date: June 17, 1996
Creator: Imrich, K.J. & Chandler, G.T.
Partner: UNT Libraries Government Documents Department

Status of irradiations performed by testing and irradiation services for BNW as of March 10, 1968

Description: This report itemizes the irradiations performed by Testing and Irradiation Services for Battelle-Northwest. It lists the material being irradiated, awaiting disposition and material shipped during the report period. Specific data given is TISR No., Request number, Material, Piece number, operating time, CMK Absorbed, charge date, location, exposure to date, discharge date and time, and shipping date.
Date: March 25, 1968
Creator: Barker, L.V.
Partner: UNT Libraries Government Documents Department

Fabrication of biaxially textured templates for coated conductors by inclined substrate deposition.

Description: YBCO-coated conductors will enable the development of smaller, lighter, more-efficient electric power devices that can be operated at temperatures approaching that of liquid nitrogen. The critical current density (J{sub c}) of YBCO films on flexible metallic substrates has been significantly improved by epitaxially growing the YBCO on biaxially textured template films. Inclined substrate deposition (ISD) offers the potential for rapidly producing high-quality biaxially textured buffer layers that are suitable for YBCO-coated conductors. Using the ISD method, we have grown biaxially textured MgO films at deposition rates of 20-100 {angstrom}/sec. Electron microscopy of the ISD-MgO films revealed columnar grains topped off by MgO (002) planes, and X-ray pole figure analysis showed that the (002) planes are tilted with respect to the substrate normal, giving ISD-MgO films a roof-tile surface morphology. A small phi-scan full-width at half maximum of {approx}10{sup o} was observed on ISD-MgO films deposited with a substrate inclination of 55{sup o}. YBCO films were grown on ISD-MgO buffered Hastelloy substrates by pulsed laser deposition. A sample that was 0.42 {micro}m x 0.45 mm x 1 cm gave a transport J{sub c} of {approx}0.34 MA/cm{sup 2} at 77 K in self-field. Details of ISD-MgO film fabrication and characterization, as well as the results of YBCO deposited on the ISD-MgO architecture, are presented.
Date: August 21, 2002
Creator: Dorris, S. E.; Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Erck, R. 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

Passive Corrosion Behavior of Alloy 22

Description: Alloy 22 (NO6022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nano-meters per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.
Date: January 20, 2006
Creator: Rebak, R.B. & Payer, J.H.
Partner: UNT Libraries Government Documents Department

RIP Input Tables from WAPDEG for LA Design Selection: Enhanced Design Alternative II-3

Description: The purpose of this calculation is to document (1) the Waste Package Degradation (WAPDEG) version 3.09 (CRWMS M&O 1998b. ''Software Routine Report for WAPDEG'' (Version 3.09)) simulations used to analyze degradation and failure of 2-cm thick titanium grade 7 corrosion resistant material (CRM) drip shields (that are placed over waste packages composed of a 2-cm thick Alloy 22 corrosion resistant material (CRM) as the outer barrier and an unspecified material to provide structural support as the inner barrier) as well as degradation and failure of the waste packages themselves, and (2) post-processing of these results into tables of drip shield/waste package degradation time histories suitable for use as input into the Integrated Probabilistic Simulator for Environmental Systems (RIP) version 5.19.01 (Golder Associates 1998) computer code. This calculation supports Performance Assessment analysis of the License Application Design Selection (LADS) Enhanced Design Alternative (EDA) II-3. The aging period in the EDA II design (CRWMS M&O 1999f. ''Design Input Request for LADS Phase II EDA Evaluations'', Item 1 Row 9 Column 3) was replaced in the case of EDA II-3 with 25 years preclosure ventilation, leading to a total of 50 years preclosure ventilation. The waste packages are line loaded in the repository and no backfill is used.
Date: August 24, 1999
Creator: Monib, A.M.
Partner: UNT Libraries Government Documents Department