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Modelagem da fratura por corrosão sob tensão nos bocais do mecanismo de acionamento das barras de controle de reator de água pressurizada"; Modeling of primary water stress corrosion cracking at control rod drive mechanism nozzles of Pressurized Water Reactors

Aly, Omar Fernandes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/06/2006 PT
Relevância na Pesquisa
96.74%
Um dos principais mecanismos de falha que causam riscos de fratura a reatores de água pressurizada é a corrosão sob tensão de ligas metálicas em água do circuito primário (CSTAP). É causada por uma combinação das tensões de tração, meio ambiente em temperatura e microestruturas metalúrgicas susceptíveis. Ela pode ocorrer, dentre outros locais, nos bocais do mecanismo de acionamento das barras de controle. Essa fratura pode causar acidentes que comprometem a segurança nuclear através do bloqueio das barras de controle e vazamentos de água do circuito primário reduzindo a confiabilidade e a vida útil do reator. O objetivo desta Tese de Doutorado é o estudo de modelos e uma proposta de modelagem para fraturas por corrosão sob tensão em liga 75Ni15Cr9Fe (liga 600), em água de circuito primário de reator de água pressurizada nesses bocais. São superpostos modelos eletroquímicos e de mecânica da fratura e validados com dados obtidos em experimentos e na literatura. Na parte experimental foram utilizados resultados obtidos pelo CDTN no equipamento recém-instalado de ensaio por taxa de deformação lenta. Na literatura está proposto um diagrama que exprime a condição termodinâmica de ocorrerem diversos modos de CSTAP na liga 600: partiu-se de diagramas de potencial x pH (diagramas de Pourbaix)...

Desenvolvimento de um dispositivo para ensaio de corrosão sob tensão : aplicação para ferro fundido cinzento imerso em biodiesel B100 de soja; Development of a device for testing stress corrosion : application to gray iron on exposure to soy biodiesel B100

Flávio Lima de Oliveira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/07/2010 PT
Relevância na Pesquisa
66.58%
Neste trabalho propôs-se o projeto de um dispositivo apropriado para ensaio de corrosão sob tensão do tipo tração com deformação constante, que seja eficiente, simples e de baixo custo. A utilização deste equipamento em ensaios de corrosão sob tensão permite avaliar as propriedades de resistência dos materiais ensaiados com relação à tensão em meios agressivos. Em adição, realizou-se um estudo comparativo sob o ponto de vista da corrosão sob tensão de amostras de ferro fundido cinzento, confeccionadas a partir de camisas de cilindro utilizadas no motor MWM Acteon X12 ciclo Diesel, que permaneceram tensionadas e expostas ao Biodiesel B100 de soja e diesel mineral derivado de petróleo. Essas amostras foram avaliadas quanto à perda de massa em função do tempo de exposição ao meio corrosivo, e inspecionadas visualmente quanto a eventual ocorrência de trincas na superfície dos corpos de prova. Comparando-se os resultados de perda de massa percentual dos corpos de prova expostos ao biodiesel B100 de soja em relação aos corpos de prova expostos ao diesel mineral, conclui-se que não houve diferença significativa nos valores apresentados que pudesse caracterizar, dentro das condições de ensaio estabelecidas...

Electrochemical impedance and current fluctuations analysis during slow strain rate test of a UNS S30400 stainless steel in low pH media

Bastos,Ivan N.; Nogueira,Ricardo P.; Ponciano,José A. C.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
66.56%
This paper is aimed at investigating the electrochemical behavior of austenitic stainless steel UNS S30400 under stress corrosion cracking conditions in acidic solutions at room temperature. Electrochemical impedance spectroscopy and electrochemical current noise measurements were performed at different stress levels during slow strain rate tests at pH 0.00 and 1.00 in order to evaluate the influence of mechanical deformation on the evolution of the electrochemical responses of the interface. Results have shown that, differently to what happens at pH 1.00, the corrosive attack at pH 0.00 is characterized by intensive cracking concomitantly to the progressive spreading out of uniform corrosion on the metallic surface. The coupling of both electrochemical impedance and current noise techniques provided complementary information about the interplay between dissolution and cracking of the stainless steel exposed to electrolytes of different aggressiveness.

Susceptibility to Stress Corrosion Cracking of 254SMO SS

De Micheli,Lorenzo; Agostinho,Silvia Maria Leite; Trabanelli,Giordano; Zucchi,Fabrizio
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2002 EN
Relevância na Pesquisa
96.62%
The susceptibility to stress corrosion cracking (SCC) of solubilized and sensitized 254SMO SS was studied in sodium chloride, and sodium fluoride solutions at 80 °C and sulfuric acid solutions in presence of sodium chloride at 25 °C. The influence of salt concentration, pH values and the addition of thiosulfate was examined. The susceptibility to SCC was evaluated by Slow Strain Rate Tests (SSRT), at 1.5 x 10-6 s-1 strain rate. The behavior of 254SMO was compared to those of AISI 316L SS and Hastelloy C276. 254SMO showed an excellent resistance to SCC in all conditions, except in the more acidic solutions (pH <= 1) where, in the sensitized conditions, intergranular stress corrosion cracking occurred.

Stress Corrosion Cracking of Zircaloy-4 in Halide Solutions: Effect of Temperature

Farina,S.B.; Duffo,G.S.; Galvele,J.R.
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2002 EN
Relevância na Pesquisa
96.51%
Zircaloy-4 was found to be susceptible to stress corrosion cracking in 1 M NaCl, 1 M KBr and 1 M KI aqueous solutions at potentials above the pitting potential. In all the solutions tested crack propagation was initially intergranular and then changed to transgranular. The effect of strain rate and temperature on the SCC propagation was investigated. An increase in the strain rate was found to lead to an increase in the crack propagation rate. The crack propagation rate increases in the three solutions tested as the temperatures increases between 20 and 90 °C. The Surface-Mobility SCC mechanism accounts for the observation made in the present work, and the activation energy predicted in iodide solutions is similar to that found in the literature.

A continuum damage model for the stress corrosion cracking of austenitic stainless steel

Bastos,I. N.; Vasconcellos,J. F. V.; Gomes,J. A. C. P.; Costa-Mattos,H. S. da
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
96.63%
In the present work, the mechanical behavior of stress corrosion cracking phenomenon is described. Such phenomenon presents strong complexity due to metallurgic and electrochemical aspects. A methodology for modeling both SSR (Slow Strain Rate) and CL (Constant Load) tests based upon thermodynamics of continuum solids and elastoplastic damage is proposed. In this macroscopic approach, besides the classical variables (stress, total strain, plastic strain), an additional scalar variable related to the damage induced by stress corrosion is introduced. An evolution law depending on the corrosive environment parameters is proposed for this damage variable. The model accounts for the stress corrosion effect through a reduction of the mechanical resistance of the material induced by the damage variable. The model prediction is compared with the curves obtained experimentally in different acid solutions at room temperature showing a good agreement. The alloy/environment system studied here is an AISI 304 austenitic stainless steel in acid aqueous solution containing sodium chloride.

Stress corrosion cracking and hydrogen embrittlement of thick section high strength low alloy steel

Needham, William Donald
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 277 leaves
ENG
Relevância na Pesquisa
86.75%
An experimental study was conducted to evaluate the corrosion performance of weldments of a high strength low alloy(HSLA) steel in a simulated seawater environment. This steel, designated HSLA80, was developed by the United States Navy for use in ship structural applications. Stress corrosion CRACKING(SCC) and hydrogen embrittlement(HEM) were investigated by conducting 42 Wedge-Opening load(WOL) tests as a function of stress intensity and corrosion potential and 33 Slow Strain Rate(SSR) tests as a function of strain rate and corrosion potential. The corrosion potentials were chosen to simulate the environmental conditions of free corrosion, cathodic protection and hydrogen generation. The results from this investigation indicated that HSLA 80 base metal and weldments were susceptible to hydrogen assisted cracking(HAC) in a seawater environment under conditions of continuous plastic deformation and triaxial stress in the presence of hydrogen. The heat-affected zone of the weldment was found to be the most susceptible portion of the weld joint. A lower bound was established for the critical stress intensity for stress corrosion cracking for HSLA 80 base metal and weldments.; by William Donald Needham.; Thesis (Ocean E.)--Massachusetts Institute of Technology...

Experiments to explore the mechanisms of stress corrosion cracking.

Gao, Jie (1984 - ); Quesnel, David J.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xvi, 147 p.; Illustrations:ill. (some col.)
ENG
Relevância na Pesquisa
66.56%
Thesis (Ph. D.)--University of Rochester. Materials Science Program, 2011.; Stress corrosion cracking (SCC) is a type of subcritical cracking of materials that occurs when a SCC susceptible material is simultaneously stressed in tension (applied or residual) and exposed to a specific corrosive environment. Failure of materials due to SCC could occur at stress levels much lower than the allowable service stress, causing catastrophic consequences. Decades of efforts to investigate the SCC phenomena have established the general behaviors of different materials during SCC and it is widely accepted that a susceptible material, tensile stress, and a specific corrosive environment are the prerequisites for the occurrence of SCC. However, the fundamental mechanisms behind the apparent SCC behaviors remain unclear mainly due to contradictory experimental data from different researchers, the intrinsic difficulties associated with material characterization within the restricted geometry of cracks, and the complexity of the interactions between different chemical species. In this thesis, attention is focused on a single material system, AA5083 aluminum alloy, where the SCC can be made to happen quickly so that the effects of various aspects on SCC can be examined within reasonable amounts of time...

Failure of a super duplex stainless steel reaction vessel

Linton, V.; Laycock, N.; Thomsen, S.; Klumpers, A.
Fonte: Pergamon-Elsevier Science Ltd Publicador: Pergamon-Elsevier Science Ltd
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
66.43%
Crevice corrosion and stress corrosion cracking (SCC) were recently discovered in a vessel used to strip vinyl chloride monomer from a water-based slurry of PVC granules. The vessel was manufactured from UNS S32750 super duplex stainless steel and the welds were produced using matching welding consumables. Although localised corrosion might have been expected, the occurrence of SCC was inconsistent with the majority of the published literature: in particular, the nominal operating temperature should have been too low for chloride-induced SCC of super-duplex stainless steel. However, damage was found mainly in the vicinity of the circumferential and longitudinal welds, and part of the subsequent failure investigation was therefore focused on the possibility of poor weld quality being the cause of failure. This task was approached primarily by measuring the influence of welding parameters on the value of the critical pitting temperature (CPT), and attempting to correlate the results with observed changes in the weld microstructure. CPT values were determined by a potentiodynamic method, using samples cut from the failed vessel and from a range of reference welds manufactured using known welding parameters.; http://www.elsevier.com/wps/find/journaldescription.cws_home/30190/description#description

An investigation of residual stress, hardness, and texture on stress corrosion cracking in a gas pipeline

Law, M.; Luzin, V.; Linton, V.; Gamboa, E.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
96.57%
Stress Corrosion Cracking, SCC, may be a serious problem in gas pipelines. This work studies the hardness and residual stress profiles in two nominally identical sections of adjacent pipe with similar environment and coating, one of which was affected by detectable SCC and the other that was not. The results show changes in texture, residual stress, plastic strain, and hardness at the pipe surface which may be responsible for the altered susceptibility to SCC.; Michael Law, Vladimir Luzin, Valerie Linton, and Erwin Gamboa

Irradiation-Assisted Stress Corrosion Cracking of Heat-Affected Zones of Austenitic Stainless Steel Welds

STOENESCU Raluca; CASTANO Maria Luisa; VAN DYCK Steven; ROTH Armin; VAN DER SCHAAF Bob; OHMS Carsten; GAVILLET D.
Fonte: The Minerals, Metals & Materials Society Publicador: The Minerals, Metals & Materials Society
Tipo: Contributions to Conferences Formato: Online
ENG
Relevância na Pesquisa
66.55%
Irradiation assisted stress corrosion cracking is known to appear in the internal components of boiling water reactors such as core shrouds. Although the behaviour of austenitic stainless steels base material has been thoroughly investigated, few studies were dedicated to the weld metal and heat affected zones (HAZ). The goal of this study is a contribution to better understand the welding and neutron-irradiation induced changes in the HAZ that may promote intergranular cracking. The evolution of residual stresses, microstructure, microchemistry, mechanical properties, and the stress corrosion behaviour of two welded austenitic stainless steels have been investigated, before and after irradiation. Slow Strain Rate Tensile (SSRT) tests were performed. Flat tensile samples, containing the weld and HAZ were fabricated from type AISI 304 and AISI 347 stainless steels. SSRT corrosion tests were performed at 290ºC in low conductivity water with 200 ppb dissolved oxygen. Reference tests were performed in inert gas (argon). The irradiated HAZs presents typical irradiation-induced defects with slightly increased density. The tensile tests reveal a significant hardening of the material that is clearly related to the irradiation induced microstructure. Finally no intergranular fracture is observed for the irradiation dose and deformation conditions studied.; JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Management

Laser peening for mitigation of stress corrosion cracking at welds in marine aluminum

Mattern, Heather R.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Relevância na Pesquisa
66.51%
This work examines the use of laser peening (LP) for mitigation of stress corrosion cracking (SCC) in marine grade aluminum alloys (Al-Mg). These alloys can be sensitized during welding and will develop a tensile residual stress in the heat affected zone that may promote SCC in a salt water environment. Metal inert gas welded aluminum alloy 5083 (4.8wt% Mg) plate was laser peened using a variety of laser intensities to create compressive stresses. Mechanical tests were performed to investigate the SCC of the material including slow strain rate testing and potentiostatically driven, salt-water exposure. Microstructural and micromechanical tests were performed to characterize the effects of LP on the microstructure of the material. The slow strain rate testing showed a systematic decrease in ductility with increasing LP intensity. The fracture surfaces on all welded samples were indicative of ductile fracture but with a pre-crack length that scaled inversely with LP intensity. The hardness of the material increased with LP intensity. This work suggests that welded aluminum alloy 5083 does not readily stress corrosion crack. LP does affect the mechanical behavior of the material, but its full effect on stress corrosion behavior requires further study.

The Effect of Sensitization on the Stress Corrosion Cracking of Aluminum Alloy 5456

Cormack, Emily C.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Relevância na Pesquisa
66.67%
This work examines the effect of sensitization on the stress corrosion cracking behavior of marine grade aluminum alloys (Al-Mg). These alloys can be sensitized during operation, promoting their susceptibility to intergranular stress corrosion cracking (IGSCC). Aluminum alloy 5456-H116 (also identified as Al-Mg5.1) samples were sensitized at 175C for varying durations of time and then mechanically tested in salt water. Mass loss tests quantified the degree of sensitization (DOS) as a function of sensitization time. Dual cantilever beam tests were used to measure the SCC growth rate and cyclic fatigue tests were conducted to determine the corrosion fatigue behavior. DOS increased as sensitization time increased with little difference in mass losses above 336 hours. Stress corrosion crack growth rate increased as sensitization time increased. Although the sensitization rates for AA5456-H116 were higher than for AA5083, the stress corrosion crack growth rates were significantly lower. The stress corrosion fracture surfaces showed clear showed a clearly intergranular fracture path with extensive crack branching and delamination in the transverse direction.

Stress corrosion cracking and hydrogen embrittlement of thick section high strength low alloy steel.

Needham, William Donald
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
66.73%
An experimental study was conducted to evaluate the corrosion performance of weldments of a high strength low alloy(HSLA) steel in a simulated seawater environment. This steel, designated HSLA80, was developed by the United States Navy for use in ship structural applications. Stress corrosion CRACKING(SCC) and hydrogen embrittlement(HEM) were investigated by conducting 42 Wedge-Opening load(WOL) tests as a function of stress intensity and corrosion potential and 33 Slow Strain Rate(SSR) tests as a function of strain rate and corrosion potential. The corrosion potentials were chosen to simulate the environmental conditions of free corrosion, cathodic protection and hydrogen generation. The results from this investigation indicated that HSLA 80 base metal and weldments were susceptible to hydrogen assisted cracking(HAC) in a seawater environment under conditions of continuous plastic deformation and triaxial stress in the presence of hydrogen. The heat-affected zone of the weldment was found to be the most susceptible portion of the weld joint. A lower bound was established for the critical stress intensity for stress corrosion cracking for HSLA 80 base metal and weldments.(Theses)

Investigation of the stress corrosion cracking susceptibility of annealed and heat treated alloy 625 castings and forgings in sea water

Jones, Eric Merwin
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
66.66%
The author hereby grants to the United States Navy, Wyman Gordon, and M.I.T. permission to reproduce and distribute copies of this thesis document in Whole or in part.; Alloy 625, the nickel based superalloy commonly called Inconel* 625, was investigated for its susceptibility to stress corrosion cracking in sea water using the slow strain rate tensile test method. Four microstructures of the alloy commonly found in end products were investigated. Bimetallic couplings with other metals were simulated with a potentiostat at plus and minus one volt with respect to a saturated standard calomel electrode (SCE). Baseline tests were conducted in air and sea water without applied potential. The response of the alloy to cathodic protection of minus three volts SCE was also investigated on the two most commonly used microstructures, as cast" and "forged/annealed". The different microstructures developed were characterized with a scanning electron microscope (SEM). The gage lengths, fracture surfaces, and sections of test specimens were also examined with a SEM. The data from the slow strain rate tensile tests were compared with data from standard tensile tests performed on the same processed material. The results from this investigation indicate that Alloy 625 is not susceptible to stress corrosion cracking in the normal sea water service environment where temperatures are close to ambient. However...

Fisuración inducida por hidrógeno de aceros soldables microaleados: caracterización y modelo de comportamiento

Álvarez Laso, José Alberto
Fonte: Universidad de Cantabria Publicador: Universidad de Cantabria
Tipo: Tese de Doutorado
SPA
Relevância na Pesquisa
66.66%
RESUMEN: Las condiciones ambientales de trabajo de los aceros estructurales y de conducciones en instalaciones energéticas y petrolíferas han puesto en evidencia la necesidad de encontrar una metodología de caracterización de su resistencia a la fisuración, tanto en régimen de dominio elástico como elastoplástico. Este trabajo recoge una metodología experimental y analítica adecuada para ser aplicada a los procesos de fisuración estudiados sobre probetas y estructuras, en particular a aquéllos asociados a la presencia de ambientes agresivos, como corrosión bajo tensión o fisuración inducida por hidrógeno de aceros microaleados. Una vez aplicada y validada, la metodología ofrece resultados de gran interés en la caracterización cuantitativa del comportamiento de fisuración y su correlación con los micromecanismos de rotura presentes. Esta tesis se ha mostrado eficaz en la caracterizacióny establecimiento de un modelo de comportamiento de aceros microaleados utilizados en condiciones de fisuración inducida por hidrógeno, como es el caso de las plataformas petrolíferas en alta mar (estructuras off-shore).; ABSTRACT: The environmental conditions of employment of structural steel and energy pipelines and oil facilities have highlighted the need to find a methodology for characterizing their resistance to cracking...

Effects of microstructure and local mechanical fields on intergranular stress corrosion cracking of a friction stir welded aluminum–copper–lithium 2050 nugget

DHONDT, Matthieu; AUBERT, Isabelle; SAINTIER, Nicolas; OLIVE, Jean-Marc
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN
Relevância na Pesquisa
86.56%
The effects of the microstructure and mechanical fields on intergranular stress corrosion cracking (IGSCC) of the nugget zone of heat treated welds obtained by friction stir welding in the AA2050 aluminum alloy have been investigated at different scales. At low strain rate, in 1.0 NaCl aqueous solution, IGSCC develops in the microstructure, whereas only pitting corrosion is observed without any mechanical stress. Based on surface observations, EBSD analysis and X-ray tomography, the key role of sub-millimetric textured bands (induced by the welding process) on the IGSCC is demonstrated. Analyses at a more local scale show the grain boundary (low angle boundary, special coincident site lattice boundary or high angle boundary) do not have a significant effect on crack initiation. Crystal plasticity finite element calculations show that the threshold normal stress at grain boundaries for IGSCC development is about 80% of the macroscopic stress. It is also highlighted by crystal plasticity calculations that there is a drastic effect of the local stress field on the shape of cracks. Finally, it is shown that plasticity induced residual stresses are sufficient for the formation of IGSCC. © 2014 Elsevier Ltd.

Degradación ambiental de las propiedades mecánicas de fibras monocristallinas de circona dopada con erbia; Environmental degradation of the mechanical properties of single-crystal erbia-doped zircona fibers

Orera, V. M.; Pastor, José Y.; Ridruejo, A.; Llorca, Javier; Sayir, Ali
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 421237 bytes; application/pdf
SPA
Relevância na Pesquisa
66.43%
[ES] Partiendo de fibras monocristalinas de ZrO2(Er2O3) tetragonal fabricadas por un procedimiento de fusión zonal con láser (LHFZ), se efectuaron ensayos de flexión en los que se medía la resistencia mecánica en función de la temperatura (25 a 800ºC) y el medio (aire o agua). Los ensayos fueron realizados a distintas velocidades con objeto de establecer la susceptibilidad a las condiciones ambientales. La susceptibilidad ambiental de la ZrO2(Y2O3) se había asociado siempre a la desestabilización de la fase tetragonal, pero el análisis de las superficies de fractura mediante microscopía electrónica de barrido y espectroscopia Raman confocal muestran una ausencia completa de fase monoclínica en las superficies de fractura de las fibras. Esta ausencia, junto con los ensayos complementarios sobre fibras sometidas a tratamientos de recocido para eliminar las tensiones residuales provenientes del procesado, indican que el crecimiento subcrítico de grieta se debe a un mecanismo de corrosión bajo tensión.; [EN] The flexure strength of tetragonal ZrO2(Er2O3) single-crystal monofilaments manufactured by the laser-heated floating zone method was measured as a function of the environment (air vs. water) and temperature (from 25 to 800ºC) at loading rates spanning three orders of magnitude to ascertain their susceptibility to the environmental conditions. These mechanical tests were completed with parallel tests on fully-annealed monofilaments (to relieve the thermal residual stresses induced during growth) and by detailed analysis of the fracture surfaces using scanning electron microscopy and micro-Raman spectroscopy. While environmental susceptibility of ZrO2(Y2O3) in previous investigations was always associated with the destabilization of the tetragonal phase...

Localized corrosion of zirconium and zircaloy- 4 in iodine alcoholic solutions

Farina,S. B.; Duffo,G. S; Galvele,J. R.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2002 EN
Relevância na Pesquisa
76.43%
The stress corrosion cracking (SCC) susceptibility of zirconium and one of its alloys, Zircaloy-4, was studied in 10 g/L iodine dissolved in various alcohols: methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol. SCC was observed in all the systems studied and the crack propagation rate was found to vary depending on the size of the solvent molecule. When the molecular weight of the solvent molecule increased, the crack propagation rate decreased. Intergranular attack was also found in all the solutions tested, and the rate of intergranular corrosion also varied with the size of the solvent molecule. This behavior is attributed to a steric effect, which hinders the access of the corrosive species to the tip of the crack. The results found agree with the predictions of the surface mobility-SCC mechanism.

Semiconductor Electrochemistry and Localised Corrosion

Rangel,C.M.; Belo,M. da Cunha
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2004 EN
Relevância na Pesquisa
76.43%
In the present work, the electronic structure of the passive film formed on austenitic stainless steel of the 304 type and its implications on the initiation of localised corrosion are investigated taking into account concepts developed in semiconductor physics and semiconductor electrochemistry. Capacitance measurements (Mott-Schottky approach), show that the susceptibility of AISI 304 stainless steel to stress corrosion cracking (SCC) in boiling chloride containing aqueous solutions is closely linked to the formation of a chromium rich passive oxide film with p-type semiconductivity. A small polarisation is required to drastically change the electric field at the film-electrolyte interface, as a consequence of the high doping level of the passive film. Initiation of the SCC phenomenon is described as the consequence of localised changes in the semiconductive properties of the passive film.