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Oxidation in a temperature gradient

Description: The effects of a temperature gradient and heat flux on point defect diffusion in protective oxide scales were examined. Irreversible thermodynamics were used to expand Fick's first law of diffusion to include a heat flux term--a Soret effect. Oxidation kinetics were developed for the oxidation of cobalt and for nickel doped with chromium. Research in progress is described to verify the effects of a heat flux by oxidizing pure cobalt in a temperature gradient above 800 C, and comparing the kinetics to isothermal oxidation. The tests are being carried out in the new high temperature gaseous corrosion and corrosion/erosion facility at the Albany Research Center.
Date: January 1, 2001
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr. & Russell, James H.
Partner: UNT Libraries Government Documents Department

Hot Corrosion at Air-Ports in Kraft Recovery Boilers

Description: Hot corrosion can occur on the cold-side of airports in Kraft recovery boilers. The primary corrosion mechanism involves the migration of sodium hydroxide and potassium hydroxide vapors through leaks in the furnace wall at the airports and their subsequent condensation. It has been reported that stainless steel is attacked much faster than carbon steel in composite tubes, and that carbon steel tubing, when used with a low-chromium refractory, does not exhibit this type of corrosion. For hot corrosion fluxing of metal oxides, either acidic or basic fluxing takes place, with a solubility minimum at the basicity of transition between the two reactions. For stainless steel, if the basicity of the fused salt is between the iron and chromium oxide solubility minima, then a synergistic effect can occur that leads to rapid corrosion. The products of one reaction are the reactants of the other, which eliminates the need for rate-controlling diffusion. This effect can explain why stainless steel is attacked more readily than carbon steel.
Date: January 1, 2003
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr. & Russell, James H.
Partner: UNT Libraries Government Documents Department

State-of-the-art review of electrochemical noise sensors

Description: There are a number of different techniques capable of being used to measure corrosion within equipment. The most simple, the use of metal coupons, usually causes the process to be shut down, is manpower intensive, and has a time delay in getting the required corrosion information. Electrical Resistance (ER) techniques are often used but their response is very sensitive to temperature and they cannot differentiate between general and localized corrosion. Electrochemical techniques, such as linear polarization resistance (LPR), electrochemical noise (EN), electrochemical impedance spectroscopy (EIS), harmonic distortion analysis (HDA), and electrochemical frequency modulation (EFM), have the capability of solving most of those drawbacks. Electrochemical probes can be mounted permanently in most equipment, give regular measurements of the intensity of corrosion, and some can detect localized corrosion. Of all of the electrochemical techniques, EN has the most potential for being used successfully to measure general and localized corrosion rates of equipment. The EN technique was studied in the late 1970s and early 80s as a means of detecting localized (stochastic) corrosion phenomena, such as occurs with pitting, crevice and cavitation attack. EN measurements are based on fluctuations in electrochemical potential and corrosion current that occur during corrosion. Electrochemical potential is related to the driving force (thermodynamics) of the reaction, while corrosion current is related to the rate of reaction (kinetics) of the reaction. The idea is that random electrochemical events on the surface of a corroding metal will generate noise in the overall potential and current signals. Each type of corrosion (for example general corrosion, pitting corrosion, crevice corrosion, and stress corrosion cracking) will have a characteristic “fingerprint” or “signature” in the signal noise. This “fingerprint” can be used to predict the type and severity of corrosion that is occurring. By comparison, conventional electrochemical techniques such as LPR, EIS, HDA and ...
Date: September 1, 2001
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr. & Eden, D. (Intercorr International)
Partner: UNT Libraries Government Documents Department

Corrosion probes for fireside monitoring in coal-fired boilers

Description: Corrosion probes are being developed and combined with an existing measurement technology to provide a tool for assessing the extent of corrosion of metallic materials on the fireside in coal-fired boilers. The successful development of this technology will provide power plant operators the ability to (1) accurately monitor metal loss in critical regions of the boiler, such as waterwalls, superheaters, and reheaters; and (2) use corrosion rates as process variables. In the former, corrosion data could be used to schedule maintenance periods and in the later, processes can be altered to decrease corrosion rates. The research approach involves laboratory research in simulated environments that will lead to field tests of corrosion probes in coal-fired boilers. Laboratory research has already shown that electrochemically-measured corrosion rates for ash-covered metals are similar to actual mass loss corrosion rates. Electrochemical tests conducted using a potentiostat show the corrosion reaction of ash-covered probes at 500?C to be electrochemical in nature. Corrosion rates measured are similar to those from an automated corrosion monitoring system. Tests of corrosion probes made with mild steel, 304L stainless steel (SS), and 316L SS sensors showed that corrosion of the sensors in a very aggressive incinerator ash was controlled by the ash and not by the alloy content. Corrosion rates in nitrogen atmospheres tended to decrease slowly with time. The addition of oxygen-containing gases, oxygen and carbon dioxide to nitrogen caused a more rapid decrease in corrosion rate, while the addition of water vapor increased the corrosion rate.
Date: January 1, 2005
Creator: Covino, Bernard S., Jr.; Bullard, Sophie J.; Ziomek-Moroz, M. & Holcomb, Gordon R.
Partner: UNT Libraries Government Documents Department

High temperature electrochemical corrosion rate probes

Description: Corrosion occurs in the high temperature sections of energy production plants due to a number of factors: ash deposition, coal composition, thermal gradients, and low NOx conditions, among others. Electrochemical corrosion rate (ECR) probes have been shown to operate in high temperature gaseous environments that are similar to those found in fossil fuel combustors. ECR probes are rarely used in energy production plants at the present time, but if they were more fully understood, corrosion could become a process variable at the control of plant operators. Research is being conducted to understand the nature of these probes. Factors being considered are values selected for the Stern-Geary constant, the effect of internal corrosion, and the presence of conductive corrosion scales and ash deposits. The nature of ECR probes will be explored in a number of different atmospheres and with different electrolytes (ash and corrosion product). Corrosion rates measured using an electrochemical multi-technique capabilities instrument will be compared to those measured using the linear polarization resistance (LPR) technique. In future experiments, electrochemical corrosion rates will be compared to penetration corrosion rates determined using optical profilometry measurements.
Date: September 1, 2005
Creator: Bullard, Sophie J.; Covino, Bernard S., Jr.; Holcomb, Gordon R. & Ziomek-Moroz, M.
Partner: UNT Libraries Government Documents Department

Thermal Spray Coatings for Coastal Infrastructure

Description: Several protection strategies for coastal infrastructure using thermal-spray technology are presented from research at the Albany Research Center. Thermal-sprayed zinc coatings for anodes in impressed current cathodic protection systems are used to extend the service lives of reinforced concrete bridges along the Oregon coast. Thermal-sprayed Ti is examined as an alternative to the consumable zinc anode. Sealed thermal-sprayed Al is examined as an alternative coating to zinc dust filled polyurethane paint for steel structures.
Date: November 1, 1997
Creator: Holcomb, G.R.; Covino, Bernard S., Jr.; Cramer, S. D. & Bullard, S. J.
Partner: UNT Libraries Government Documents Department

Analysis of Staining Observed on Structures in the Georgetown, South Carolina Area

Description: Beginning around 1970, the Georgetown, SC, community complained about black dust and red stains collecting on houses, cars, boats, and other structures. The community, through the South Carolina Department of Health and Environmental Control (SCDHEC), seeks to identify the source or cause of the staining and ways to reduce or eliminate it in the future.
Date: May 2002
Creator: Cramer, Stephen D.; Covino, Bernard S., Jr. & Govier, R. Dale
Partner: UNT Libraries Government Documents Department

Thermal-sprayed zinc anodes for cathodic protection of steel-reinforced concrete bridges

Description: Thermal-sprayed zinc anodes are being used in Oregon in impressed current cathodic protection (ICCP) systems for reinforced concrete bridges. The U.S. Department of Energy, Albany Research Center, is collaborating with the Oregon Department of Transportation (ODOT) to evaluate the long-term performance and service life of these anodes. Laboratory studies were conducted on concrete slabs coated with 0.5 mm (20 mil) thick, thermal-sprayed zinc anodes. The slabs were electrochemically aged at an accelerated rate using an anode current density of 0.032 A/m2 (3mA/ft2). Half the slabs were preheated before thermal-spraying with zinc; the other half were unheated. Electrochemical aging resulted in the formation at the zinc-concrete interface of a thin, low pH zone (relative to cement paste) consisting primarily of ZnO and Zn(OH)2, and in a second zone of calcium and zinc aluminates and silicates formed by secondary mineralization. Both zones contained elevated concentrations of sulfate and chloride ions. The original bond strength of the zinc coating decreased due to the loss of mechanical bond to the concrete with the initial passage of electrical charge (aging). Additional charge led to an increase in bond strength to a maximum as the result of secondary mineralization of zinc dissolution products with the cement paste. Further charge led to a decrease in bond strength and ultimately coating disbondment as the interfacial reaction zones continued to thicken. This occurred at an effective service life of 27 years at the 0.0022 A/m2 (0.2 mA/ft2) current density typically used by ODOT in ICCP systems for coastal bridges. Zinc coating failure under tensile stress was primarily cohesive within the thickening reaction zones at the zinc-concrete interface. There was no difference between the bond strength of zinc coatings on preheated and unheated concrete surfaces after long service times.
Date: January 1, 1996
Creator: Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D. & McGill, Galen E. (Oregon Dept. of Transportation)
Partner: UNT Libraries Government Documents Department

Ultra supercritical steamside oxidation

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions, which are part of the U.S. Department of Energy's Vision 21 goals. Most current coal power plants in the U.S. operate at a maximum steam temperature of 538 C. However, new supercritical plants worldwide are being brought into service with steam temperatures of up to 620 C. Vision 21 goals include steam temperatures of up to 760 C. This research examines the steamside oxidation of advanced alloys for use in USC systems. Emphasis is placed on alloys for high- and intermediate-pressure turbine sections. Initial results of this research are presented.
Date: January 1, 2004
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.; Ziomek-Moroz, M.; Alman, David A. et al.
Partner: UNT Libraries Government Documents Department

Ultra supercritical turbines--steam oxidation

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions, which are goals of the U.S. Department of Energy?s Advanced Power Systems Initiatives. Most current coal power plants in the U.S. operate at a maximum steam temperature of 538?C. However, new supercritical plants worldwide are being brought into service with steam temperatures of up to 620?C. Current Advanced Power Systems goals include coal generation at 60% efficiency, which would require steam temperatures of up to 760?C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections. Initial results of this research are presented.
Date: January 1, 2004
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.; Ziomek-Moroz, Margaret & Alman, David E.
Partner: UNT Libraries Government Documents Department

Monitoring power plant fireside corrosion using corrosion probes

Description: The ability to monitor the corrosion degradation of key components in fossil fuel power plants is of utmost importance for Futuregen and ultra-supercritical power plants. Fireside corrosion occurs in the high temperature sections of energy production facilities due to a number of factors: ash deposition, coal composition, thermal gradients, and low NOx conditions, among others. Problems occur when equipment designed for either oxidizing or reducing conditions is exposed to alternating oxidizing and reducing conditions. This can happen especially near the burners. The use of low NOx burners is becoming more commonplace and can produce reducing environments that accelerate corrosion. One method of addressing corrosion of these surfaces is the use of corrosion probes to monitor when process changes cause corrosive conditions. In such a case, corrosion rate could become a process control variable that directs the operation of a coal combustion or coal gasification system. Alternatively, corrosion probes could be used to provide an indication of total metal damage and thus a tool to schedule planned maintenance outages.
Date: January 1, 2005
Creator: Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.; Holcomb, Gordon R. & Ziomek-Moroz, M.
Partner: UNT Libraries Government Documents Department

Oxidation of alloys for advanced steam turbines

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.
Date: January 1, 2005
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D. & Ziomek-Moroz, M.
Partner: UNT Libraries Government Documents Department

Oxidation of alloys for advanced steam turbines

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.
Date: January 1, 2005
Creator: Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Ziomek-Moroz, M. & Alman, David E.
Partner: UNT Libraries Government Documents Department

Electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines

Description: The U.S. Department of Energy, National Energy Technology Laboratory funded a Natural Gas Infrastructure Reliability program directed at increasing and enhancing research and development activities in topics such as remote leak detection, pipe inspection, and repair technologies and materials. The Albany Research Center (ARC), U.S. Department of Energy was funded to study the use of electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines. As part of this, ARC entered into a collaborative effort with the corrosion sensor industry to demonstrate the capabilities of commercially available remote corrosion sensors for use with the Nation's Gas Transmission Pipeline Infrastructure needs. The goal of the research was to develop an emerging corrosion sensor technology into a monitor for the type and degree of corrosion occurring at key locations in gas transmission pipelines.
Date: September 1, 2002
Creator: Holcomb, Gordon R.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Russell, James H. & Ziomek-Moroz, Margaret
Partner: UNT Libraries Government Documents Department

Ultra Supercritical Steamside Oxidation

Description: Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions, which are goals of the U.S. Department of Energy's Advanced Power Systems Initiatives. Most current coal power plants in the U.S. operate at a maximum steam temperature of 538 C. However, new supercritical plants worldwide are being brought into service with steam temperatures of up to 620 C. Current Advanced Power Systems goals include coal generation at 60% efficiency, which require steam temperatures of up to 760 C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections. Initial results of this research are presented.
Date: January 1, 2005
Creator: Holcomb, Gordon R.; Cramer, Stephen D.; Covino, Bernard S., Jr.; Bullard, Sophie J. & Ziomek-Moroz, Malgorzata
Partner: UNT Libraries Government Documents Department

Dual-Environment Effects on the Oxidation of Metallic Interconnects

Description: Metallic interconnects in solid oxide fuel cells are exposed to a dual environment: fuel on one side (i.e., H2 gas) and oxidizer on the other side (i.e., air). It has been observed that the oxidation behavior of thin stainless steel sheet in air is changed by the presence of H2 on the other side of the sheet. The resulting dual-environment scales are flaky and more friable than the single-environment scales. The H2 disrupts the scale on the air side. A model to explain some of the effects of a dual environment is presented where hydrogen diffusing through the stainless steel sheet reacts with oxygen diffusing through the scale to form water vapor, which has sufficient vapor pressure to mechanically disrupt the scale. Experiments on preoxidized 316L stainless steel tubing exposed to air-air, H2-air, and H2-Ar environments are reported in support of the model.
Date: 2006-08~
Creator: Holcomb, Gordon R.; Ziomek-Moroz, Malgorzata; Cramer, Stephen D.; Covino, Bernard S., Jr. & Bullard, Sohpie J.
Partner: UNT Libraries Government Documents Department

Scale formation on Ni-based alloys in simulated solid oxide fuel cell interconnect environments

Description: Recent publications suggest that the environment on the fuel side of the bi-polar stainless steel SOFC interconnects changes the oxidation behavior and morphology of the scale formed on the air side. The U.S. Department of Energy Albany Research Center (ARC), has examined the role of such exposure conditions on advanced nickel base alloys. Alloy formulations developed at ARC and commercial alloys were studied using X-ray diffraction (XRD) and Raman spectroscopy. The electrical property of oxide scales formed on selected alloys was determined in terms of areaspecific resistance (ASR). The corrosion behavior of ARC nickel-based alloys exposed to a dual environment of air/ H2 were compared to those of Crofer 22APU and Haynes 230.
Date: November 1, 2004
Creator: Ziomek-Moroz, Margaret; Cramer, Stephen D.; Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Singh, P. (PNNL) et al.
Partner: UNT Libraries Government Documents Department

Understanding the corrosion behavior of chromia-forming 316L stainless steel in dual oxidizing-reducing environment representative of SOFC interconnect

Description: A and B site doped LaCrO3-based electronically conducting Perovskite ceramic materials have been extensively used as interconnects in solid oxide fule cells (SOFC) operating at 800° to 1000°C as the Perovskites offer good electrical conductivity, chemical compatibility with the adjacent components of the fuel cell, chemical stability in reducing and oxidizing atmospheres, and thermal expansion coefficients that match other cell components. However, requirements for good mechanical properties, electrical and thermal conductivities, and low cost make metallic interconnects more promising. Significant progress in reducing the operating temperature of SOFC from ~1000°C to ~750°C is expected to permit the use of metallic materials with substantial cost reduction. Among the commercially available metallic materials, Cr2O3 (chromia) scale-forming iron base alloys appear to be the most promising candidates since they can fulfill the technical and economical requirements. These alloys, however, remain prone to reactions with oxygen and water vapor at fuel cell operating conditions and formation of gaseous chromium oxides and oxyhydroxides. To study the degradation processes and corrosion mechanisms of commercial chromia scale-forming alloys under SOFC interconnect exposure conditions, 316L was selected for this research because of the availability of the materials. The dual environment to which the interconnect material was exposed consisted of dry air (simulates the cathode side environment) and a mixture of H2 and 3% H2O (simulates the anode side environment). Post-corrosion surface evaluation involved the use of optical and scanning electron microscopy, as well as energy dispersive X-ray analyses.
Date: November 1, 2003
Creator: Ziomek-Moroz, Margaret; Cramer, Stephen D.; Holcomb, Gordon R.; Covino, Bernard S., Jr.; Matthes, Steven A.; Bullard, Sophie J. et al.
Partner: UNT Libraries Government Documents Department

Understanding the operation and use of high temperature electrochemical corrosion rate probes

Description: Electrochemical corrosion rate probes were constructed and tested along with mass loss coupons in a N2/O2/CO2 plus water vapor environment. Temperatures ranged from 450 to 600 C. Corrosion rates for ash-covered mild steel, 304L SS, and 316L SS probes using electrochemical techniques were a function of time, temperature, and process environment. Correlation between electrochemical and mass loss corrosion rates was good.
Date: January 1, 2004
Creator: Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.; Holcomb, Gordon R.; Ziomek-Moroz, M.; Cayard, Michael S. (InterCorr International Inc.) et al.
Partner: UNT Libraries Government Documents Department

Corrosion in a temperature gradient

Description: High temperature corrosion limits the operation of equipment used in the Power Generation Industry. Some of the more destructive corrosive attack occurs on the surfaces of heat exchangers, boilers, and turbines where the alloys are subjected to large temperature gradients that cause a high heat flux through the accumulated ash, the corrosion product, and the alloy. Most current and past corrosion research has, however, been conducted under isothermal conditions. Research on the thermal-gradient-affected corrosion of various metals and alloys is currently being studied at the Albany Research Center’s SECERF (Severe Environment Corrosion and Erosion Research Facility) laboratory. The purpose of this research is to verify theoretical models of heat flux effects on corrosion and to quantify the differences between isothermal and thermal gradient corrosion effects. The effect of a temperature gradient and the resulting heat flux on corrosion of alloys with protective oxide scales is being examined by studying point defect diffusion and corrosion rates. Fick’s first law of diffusion was expanded, using irreversible thermodynamics, to include a heat flux term – a Soret effect. Oxide growth rates are being measured for the high temperature corrosion of cobalt at a metal surface temperature of 900ºC. Corrosion rates are also being determined for the high temperature corrosion of carbon steel boiler tubes in a simulated waste combustion environment consisting of O2, CO2, N2, and water vapor. Tests are being conducted both isothermally and in the presence of a temperature gradient to verify the effects of a heat flux and to compare to isothermal oxidation.
Date: January 1, 2003
Creator: Covino, Bernard S., Jr.; Holcomb, Gordon R.; Cramer, Stephen D.; Bullard, Sophie J.; Ziomek-Moroz, Margaret & White, M.L. (Convanta)
Partner: UNT Libraries Government Documents Department

Oxidation Resistance of Low Carbon Stainless Steel for Applications in Solid Oxide Fuel Cells

Description: Alloys protected from corrosion by Cr2O3 (chromia) are recognized as potential replacements for LaCrO3–based ceramic materials currently used as bipolar separators (interconnects) in solid oxide fuel cells (SOFC). Stainless steels gain their corrosion resistance from the formation of chromia, when exposed to oxygen at elevated temperatures. Materials for interconnect applications must form uniform conductive oxide scales at 600–800o C while simultaneously exposed to air on the cathode side and mixtures of H2 - H2O, and, possibly, CHx and CO - CO2 on the anode side. In addition, they must possess good physical, mechanical, and thermal properties. Type 316L stainless steel was selected for the baseline study and development of an understanding of corrosion processes in complex gas environments. This paper discusses the oxidation resistance of 316L stainless steel exposed to dual SOFC environment for ~100 hours at ~900oK. The dual environment consisted of dry air on the cathode side of the specimen and a mixture of H2 and 3% H2O on the anode side. Post - corrosion surface evaluation involved the use of optical and scanning electron microscopy and x-ray diffraction analyses.
Date: October 1, 2003
Creator: Ziomek-Moroz, Margaret; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Cramer, Stephen D.; Bullard, Sophie J.; Matthes, Steven A. et al.
Partner: UNT Libraries Government Documents Department

High temperature corrosion research at the Albany Research Center

Description: The Severe Environment Corrosion and Erosion Research Facility (SECERF) at the Albany Research Center is operational. SECERF consists of 6 modules that share the availability of up to 10 different gases to produce environments for high temperature corrosion and erosion research. Projects to be conducted in the modules include: corrosion sensors for fossil energy systems, thermal gradient effects on high temperature corrosion, the development of sulfidation resistant alloys, determination of the effects of ash on the corrosion of metals and alloys in coal and waste combustion and coal gasification environments, high temperature erosion-corrosion of metals, and molten slag effects on refractories. Results from two areas, the effect of ash deposits on alloy corrosion and thermal gradient effects on the corrosion of metals, will be highlighted. Ash produced in coal gasifiers, coal combustors, and waste combustors, when deposited on metal surfaces, provides sites for corrosion attack and contributes chemical species that participate in the corrosion reaction. Results are presented for the corrosion of 304L stainless steel, that was either uncoated or coated with ash or with ash containing NaCl or Na2SO4, in air-water vapor mixtures at 600 C. The presence of high heat fluxes and temperature gradients in many fossil energy systems creates the need for an understanding of their effects on corrosion and oxidation. Such information would be useful for both improved alloy design and for better translation of isothermal laboratory results to field use. Temperature gradients in a solid oxide result in two changes that modify diffusion within the oxide. The first is when a gradient in point defect concentration is created within the oxide, for example, where more vacancies are expected at a higher temperature. The second change is when the presence of a temperature gradient biases the diffusion jump of an atom. Results of tests are presented ...
Date: January 1, 2002
Creator: Covino, Bernard S., Jr.; Holcomb, Gordon R.; Russell, James H.; Cramer, Stephen D.; Bullard, Sophie J.; Ziomek-Moroz, Margaret et al.
Partner: UNT Libraries Government Documents Department

Study of scale formation on AISI 316L in simulated solid oxide fuel cell bi-polar environments

Description: Significant progress made towards reducing the operating temperature of solid oxide fuel cells (SOFC) from {approx}1000 C to {approx}600 C is expected to permit the use of metallic materials with substantial cost reduction. One of the components in a SOFC stack to be made of metallic materials is a bipolar separator, also called an interconnect. It provides electrical connection between individual cells and serves as a gas separator to prevent mixing of the fuel and air. At operating temperature, the material selected for interconnects should possess good chemical and mechanical stability in complex fuel and oxidant gaseous environments, good electrical conductivity, and a coefficient of thermal expansion (CTE) that matches that of the cathode, anode, and electrolyte components. Cr2O3 scale-forming alloys appear to be the most promising candidates. There appears to be a mechanism whereby the environment on the fuel side of a stainless steel interconnect changes the corrosion behavior of the metal on the air side. The corrosion behavior of 316L stainless steel simultaneously exposed to air on one side and H2+3%H2O on the other at 907 K was studied using X-ray diffraction (XRD) and Raman spectroscopy. The electrical property of the investigated material was determined in terms of area-specific resistance (ASR). The chemical and electrical properties of 316L exposed to a dual environment of air/ (H2+H2O) were compared to those of 316L exposed to a single environment of air/air.
Date: January 1, 2004
Creator: Ziomek-Moroz, M.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Holcomb, Gordon R.; Bullard, Sophie J.; Singh (PNNL), P. et al.
Partner: UNT Libraries Government Documents Department