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Influência dos íons brometo e cloreto sobre a resistência à corrosão por pite de diferentes aços inoxidáveis austeníticos e ferríticos.; Influence of the bromide and chloride ions on pitting corrosion resistance of various austenitic and ferritic stainless steels.

Hincapié Ramírez, Alexander
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/06/2011 PT
Relevância na Pesquisa
47.718164%
A corrosão localizada em aços inoxidáveis pode se manifestar de várias formas, tais como, a corrosão por pite, em fresta e corrosão sob tensão. Estes tipos de corrosão ocorrem quando o metal é exposto em meios agressivos como o cloreto, entre outros. O objetivo deste trabalho é estudar o comportamento dos aços inoxidáveis austeníticos e ferríticos em meios agressivos de cloreto, brometo e suas misturas. Para testar a resistência à corrosão por pite foi usado o método de polarização potenciodinâmica em eletrólitos de concentração iônica total de 0,6M. Os materiais estudados foram os aços inoxidáveis: 298 (aço inoxidável Cr-Mn, especificação da ArcelorMittal Inox Brasil) e os aços padronizados segundo a UNS: S30400, S31603, S43000 e S44400; todos, na condição tal como recebida da usina. Os resultados mostraram que, em meio de 0,6M(NaCl+NaBr), para concentrações de 0M a 0,45M NaCl, o desempenho quanto a resistência à corrosão por pite obedece a seguinte ordem decrescente: 444, 316L, 304, 298 e 430. Por sua vez, para a concentração de 0,6M NaCl, ou seja, ausência total de brometo, ocorre a alteração do desempenho dos aços inoxidáveis, colocando a seqüência da seguinte ordem: 316L, 444, 304...

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
68.128228%
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
58.11458%
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...

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
67.86279%
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
67.6583%
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
68.03685%
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
68.24585%
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...

Roles of compressive residual stress in enhancing the corrosion resistance of nano nitride composite coatings on steel

Zhao, X.; Munroe, P.; Habibi, D.; Xie, Z.
Fonte: The Ceramic Society of Japan and the Korean Ceramic Society Publicador: The Ceramic Society of Japan and the Korean Ceramic Society
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
48.215166%
Nanocomposite coatings were synthesized, and subsequently annealed, in an attempt to understand the influence of residual stress upon their resistance to corrosion under acidic attack. Pitting corrosion, originating from microscopic coating defects, was commonly identified in the coatings subject to annealing. Finite element analysis was used to map the residual stress distribution adjacent to these defects and quantify resulting geometrical changes. The results show that with the presence of compressive residual stress in the coatings, corrosion-initiated cracking along weak interfaces was suppressed, and structural integrity maintained. Moreover, compressive residual stress helped constrict pre-existing structural defects in columnar-structured coatings and, in doing so, block the pathway of corrosive agents and limit corrosion damage to the coating–substrate interface and the substrate. The closure aspect ratio of the coating defects, defined as a new key indicator to the corrosion resistance, was numerically evaluated and quantitatively discussed for TiN coatings. Coating corrosion resistance may be improved by optimizing the residual stress in conjunction with coating thickness and the geometry of common defects.; Xiaoli Zhao...

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
67.842573%
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
47.79014%
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
47.911997%
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
48.15012%
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 crack detection in alloy 600 in high temperature caustic.

Brisson, Bruce W.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
47.730947%
CIVINS; Alloy 600, the material used for pressurized water reactor steam generator tubing, is susceptible to environmentally assisted stress corrosion cracking. Intergranular stress corrosion cracking (IGSCC) attacks the tubes in areas of high residual stress, and in crevice regions. No method has been successfully developed to monitor steam generator tubing in-situ for crack initiation and growth. Essentially all available published IGSCC crack growth data for alloy 600 is based on non-tubing material. Although it is very likely that the current data base is applicable to tubing processing, differences between tube and other geometries make a comparison between tubing and other data important for verification purposes. However, obtaining crack initiation and growth data from tubing is difficult due to the geometry and the thin wall thickness

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
48.18829%
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
47.86279%
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...

Effect of electro discharge machining (EDM) on the AISI316L SS white layer microstructure and corrosion resistance

SIDHOM, Habib; GHANEM, Farhat; AMADOU, Tidiane; GONZALEZ, Gonzalo; BRAHAM, Chedly
Fonte: Springer Publicador: Springer
EN
Relevância na Pesquisa
47.82591%
The localised corrosion resistance of austenitic stainless steels is strongly influenced by the quality of finished surface. EDM machining induces substantial changes by the high thermal gradients generated by electric sparks. Experimental techniques such as roughness measurement, scanning electron microscopy (SEM), energy dispersive microanalysis (EDX) and X-ray diffraction technique, reveal microgeometrical, microstructural, chemical and mechanical changes. These changes lead to white and heat-affected layers with a depth less than 100 μm. The white layer is a melted material characterised by dendritic structure and constituted by austenite, chromium carbide and ε-carbide. The heat-affected layer is characterised by very large grain size comparatively to the bulk material. Electrochemical test coupled with metallographic examinations using SEM reveals a weakening of the resistance to pitting and intergranular corrosion comparatively to diamond polished surface. This weakening is correlated to differences in structure and chemical composition of white layer. Susceptibility to stress corrosion cracking has been attributed to the field of tensile residual stresses resulting from thermal effects. The removal of the white layer material by polishing or wire brushing restores the corrosion resistance of the AISI316L SS.

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
68.063726%
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.

Evolution of anodic stress corrosion cracking in a coated material

Bjerkén, C.; Ortiz, M.
Fonte: Springer Publicador: Springer
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /10/2010
Relevância na Pesquisa
47.79014%
In the present paper, we investigate the influence of corrosion driving forces and interfacial toughness for a coated material subjected to mechanical loading. If the protective coating is cracked, the substrate material may become exposed to a corrosive media. For a stress corrosion sensitive substrate material, this may lead to detrimental crack growth. A crack is assumed to grow by anodic dissolution, inherently leading to a blunt crack tip. The evolution of the crack surface is modelled as a moving boundary problem using an adaptive finite element method. The rate of dissolution along the crack surface in the substrate is assumed to be proportional to the chemical potential, which is function of the local surface energy density and elastic strain energy density. The surface energy tends to flatten the surface, whereas the strain energy due to stress concentration promotes material dissolution. The influence of the interface energy density parameter for the solid–fluid combination, interface corrosion resistance and stiffness ratios between coating and substrate is investigated. Three characteristic crack shapes are obtained; deepening and narrowing single cracks, branched cracks and sharp interface cracks. The crack shapes obtained by our simulations are similar to real sub-coating cracks reported in the literature.

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
57.672095%
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
57.672095%
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.