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Corrosion Cracking (corrosion + cracking)
Kinds of Corrosion Cracking Selected AbstractsStress Corrosion Cracking and Hydrogen Diffusion in Magnesium,ADVANCED ENGINEERING MATERIALS, Issue 8 2006A. Atrens Evaluation of recent data for hydrogen (H) diffusion in magnesium (Mg) yielded a new equation for the diffusion coefficient of H in Mg. This indicates that there can be significant H transport ahead of a stress corrosion crack in Mg at ambient temperature and that H may be involved in the mechanism of stress corrosion cracking in Mg. [source] Numerical simulation of rotating bending process for U-tubes in heat exchangersFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 10 2009H.-S. KIM ABSTRACT Heat exchangers comprise thousands of tubes having U-shaped portions. Rotating bending method has been widely utilized to make U-bends. Although this method shows an excellent performance, cracks have been frequently detected in the U-bends due to residual stresses induced by bending. In this paper, the bending process is simulated based on elastic,plastic finite element analyses in order to investigate the magnitude and distribution of the residual stresses including the effects of operating pressure. Analyses results show that the residual stress increases as the radius of U-bend decreases and that operating pressure has a detrimental effect in terms of stress corrosion cracking at the intrados of U-bend. It is thought that these results can be utilized for the estimations of fracture mechanics parameters such as limit load, stress intensity factor and J-integral, prevention of the cracking, and establishment of the optimum inspection strategy for the heat exchanger tubes. [source] Nanoscopic fatigue and stress corrosion crack growth behaviour in a high-strength stainless steel visualized in situ by atomic force microscopyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2005K. MINOSHIMA ABSTRACT In situ atomic force microscope (AFM) imaging of the fatigue and stress corrosion (SC) crack in a high-strength stainless steel was performed, under both static and dynamic loading. The AFM systems used were (1) a newly developed AFM-based system for analysing the nanoscopic topographies of environmentally induced damage under dynamic loads in a controlled environment and (2) an AFM system having a large sample stage together with a static in-plane loading device. By using these systems, in situ serial clear AFM images of an environmentally induced crack under loading could be obtained in a controlled environment, such as in dry air for the fatigue and in an aqueous solution for the stress corrosion cracking (SCC). The intergranular static SC crack at the free corrosion had a sharp crack tip when it grew straight along a grain boundary. The in situ AFM observations showed that the fatigue crack grew in a steady manner on the order of sub-micrometre. The same result was obtained for the static SC crack under the free corrosion, growing straight along a grain boundary. In these cases, the crack tip opening displacement (CTOD) remained constant. However, as the static SC crack was approaching a triple grain junction, the growth rate became smaller, the CTOD value increased and the hollow ahead of the crack tip became larger. After the crack passed through the triple grain junction, it grew faster with a lower CTOD value; the changes in the CTOD value agreed with those of the crack growth rate. At the cathodic potential, the static SC crack grew in a zigzag path and in an unsteady manner, showing crack growth acceleration and retardation. This unsteady crack growth was considered to be due to the changes in the local hydrogen content near the crack tip. The changes in the CTOD value also agreed with those of the crack growth rate. The CTOD value in the corrosive environment was influenced by the microstructure of the material and the local hydrogen content, showing a larger scatter band, whereas the CTOD value of the fatigue crack in dry air was determined by the applied stress intensity factor, with a smaller scatter band. In addition, the CTOD value in the corrosive environment under both static and dynamic loading was smaller than that of the fatigue crack; the environmentally induced crack had a sharper crack tip than the fatigue crack in dry air. [source] Stress corrosion cracking and selective corrosion of copper-zinc alloys for the drinking water installation,MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2009E. Brandl Abstract Despite a generally good corrosion resistance to tap and industrial water, many brass taps and fittings have failed in the past by stress corrosion cracking (SCC) and selective corrosion (dezincification or preferred removal of a phase). The experimental investigations of the present study clarify the influence of the ammonia concentration on the two types of corrosion. Notched specimens made of the alloys CuZn39Pb3, CuZn40Pb2, CuZn37, CuZn36Pb2As and CuZn21Si3P are polarized anodically in pure tap water and tap water with realistic ammonia concentrations (15 and 30 ppm) under a simultaneous mechanical loading condition. The influence of stress and of the third alloying elements lead and arsenic are investigated and evaluated. The experiments show that the ammonia additions significantly increase the risk of dezincification of the ,-,-brasses. The arsenic in the CuZn36Pb2As alloy avoids dezincification, but enhances the risk of SCC. The rate of selective corrosion and SCC consistently increases with increase in tensile stress. [source] Stress corrosion cracking susceptibility of stainless steels in pulp cooking processes,online capillary electrophoresis, potentiostatic and chromatographic studiesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2008H. Leinonen Abstract An online high temperature capillary electrophoresis instrument (HotUCE), a potentiometer and an ion chromatograph were used in studies on corrosive ions and changes in potential at normal pulping process temperatures in experimental liquors modelling pulp cooking processes at mills. The aim was to evaluate the stress corrosion cracking (SCC) susceptibility of stainless steels. The HotUCE instrument and the potentiometer were online coupled with an autoclave, where welded duplex stainless steel samples were immersed for 500 h in simulated high ionic strength hot black liquor (HBL), hot white liquor (HWL) or green liquor (GL) at 130, 150 or 170,°C, respectively. The results showed that only minor amounts of oxidized sulphur compounds were formed. The concentrations of corrosive sulphur anions were calculated against sulphur standards. Amounts of sulphur species in the liquor correlated with the changes in the potential of the duplex stainless steel specimens during the cooking experiments. The formation of sulphite during cooking was greater in HWL than in HBL. Changes in the potential showed that reduction processes occurred during the SCC tests. The results indicate that the SCC risk is enhanced at higher temperatures, probably, due to the increased formation of thiosulphate. [source] Chemical composition of new copper alloys for machining and its effect on their susceptibility to corrosion crackingMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2007B. Eremiá Zinc-containing copper alloys, the so-called ,,+,, brasses, are commonly used in contact with potable water. These materials are alloyed with lead to improve machinability. In wrought special brass alloys, reducing the content of this alloying element or replacing it with alternative alloying additions may give rise to a new type of machinable copper alloys which differ from the original alloys by their contents of other modifier elements such as Si (or possibly, Mg, Bi, and P). These alloys have a very low content of lead required for the break-up of chips during machining. Even though these types of brass exhibit a very good machinability, the effects of their chemical composition on the resistance of the alloy to corrosion cracking have not yet been given sufficient attention. This paper aims to present an assessment of three new types of machinable copper alloys regarding their susceptibility to stress corrosion cracking, in comparison to that of the lead-alloyed variety, in 0.05 M NaCl, NaNO2, and Na2SO4 solutions. The slow strain rate test has been used for this purpose, and its results were correlated with metallographic evaluation of the number and depth of the cracks observed on the test specimen surfaces on completion of the test. [source] Corrosion characteristics of the wrought Ni-Cr-Mo alloysMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2005P. Crook Abstract This paper concerns the wrought, nickel-chromium-molybdenum (Ni-Cr-Mo) alloys, a family of materials with a long history of use in the chemical process industries. Their attributes include resistance to the halogen acids and resistance to pitting, crevice attack, and stress corrosion cracking in hot, halide salt solutions. The purpose of this paper is to characterize the performance of the Ni-Cr-Mo alloys in several key chemicals, using iso-corrosion diagrams. These indicate the expected corrosion rates over wide ranges of concentration and temperature. Furthermore, the differences between individual Ni-Cr-Mo alloys, and their behavior relative to the stainless steels are defined. The data indicate benefits of both a high chromium content and a copper addition, as used in Hastelloy® C-2000® alloy. [source] Theoretical description of the practical possibility of stress corrosion cracking from crevice corrosion sitesMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2005S. Wang Abstract Stress corrosion cracking (SCC) from crevice corrosion sites had been found in an experimental work at polarization potential of + 200 mVSCE. In that work, an occluded U-bend specimen of Type 316L (UNS S31603) stainless steel was used. The testing was done in sodium chloride (NaCl) solution. Based on that work, the practical possibility of SCC from the occluded U-bend specimen was described theoretically. It was shown that it would also be possible for SCC to occur in practice (i.e. at practical corrosion potential), but the crevice needs to be tighter. Meanwhile, it would take a longer time for obvious SCC to emerge. For a practical crevice usually formed by placing a crevice former on a large uniform metal surface, the crevice geometry may have little effect on SCC although the crevice can sustain an acidified solution more easily than pitting. The possibility of SCC should mainly depend on the corrosion system itself, i.e. material and environment. [source] Anion effects on the stress corrosion cracking behaviour of aluminium alloysMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 3 2003R. Braun Spannungsrisskorrosion; Aluminiumlegierungen; Chloride; halogenfreie Anionen Abstract The stress corrosion cracking behaviour of plate material of the aluminium alloys 2024-T351, 8090-T8171, 7475-T651, and 7075-T7351 was investigated performing constant load tests. Short transverse tensile specimens were permanently immersed in aerated aqueous 0.6 M Na2Cl solutions with additions of Na2SO4, NaNO3, NaHCO3, NH4HCO3, Na2HPO4, Na2SO3 or Na2CO3. The concentration of the added salts was 0.06 M. The applied stress was 100 MPa, except with 7075-T7351 specimens, which were loaded at 300 MPa. Environment induced failure was not observed in neutral 0.6 M NaCl solution. The various salts added promoted intergranular stress corrosion cracking with the alloys 2024-T351, 8090-T8171, and 7475-T651. Threshold stresses were generally below 100 MPa. For 8090-T8171 exposed to chloride containing electrolytes with additions of sulfate, hydrogen phosphate, or sulfite, threshold stresses were approximately 100 MPa or higher. Similar results were obtained for 7475-T651 plate when immersed in chloride-hydrogen phosphate and chloride-carbonate solutions. Alloy 7075-T7351 was resistant against intergranular stress corrosion cracking. Specimens suffered pitting corrosion during immersion in the corrosive environments. Failure observed with 7075-T7351, in particular when exposed to the chloride-nitrate solution, was associated with reduction of cross-sectional area due to pitting and transgranular stress corrosion cracking. Anioneneinflüsse auf das Spannungsrisskorrosionsverhalten von Aluminiumlegierungen Das Spannungsrisskorrosionsverhalten von Plattenmaterial der Aluminiumlegierungen 2024-T351, 8090-T8171, 7475-T651 und 7075-T7351 wurde in kurzer Querrichtung untersucht. Dauertauchversuche wurden unter konstanter Belastung in wässrigen 0,6 M NaCl Lösungen mit 0,06 M Zusätzen von Na2SO4, NaNO3, NaHCO3, NH4HCO3, Na2HPO4, Na2SO3 oder Na2CO3 durchgeführt. Die aufgebrachte Spannung betrug 100 MPa, außer bei Zugproben der Legierung 7075-T7351, die mit 300 MPa belastet wurden. Während bei Auslagerung in neutraler Natriumchlorid-Lösung kein Versagen beobachtet wurde, lösten die zugegebenen Salze bei den Legierungen 2024-T351, 8090-T8171 und 7475-T651 interkristalline Spannungsrisskorrosion aus. Die kritischen Grenzspannungen lagen überwiegend unter 100 MPa. Bei Auslagerung in chloridhaltigen Elektrolyten mit beigegebenen Sulfat-, Hydrogenphosphat- oder Sulfitionen waren die kritischen Grenzspannungen für die Legierung 8090-T8171 etwas höher; sie hatten einen um 100 MPa oder darüber liegenden Wert. Gleiches galt für die Legierung 7475-T651 in chloridhaltigen Lösungen mit Hydrogenphosphat- oder Carbonatzusätzen. Plattenmaterial der Legierung 7075-T7351 war in den untersuchten Elektrolyten beständig gegen interkristalline Spannungsrisskorrosion. Die Proben wurden jedoch durch Lochkorrosion geschädigt. Querschnittsverminderung infolge Lochkorrosion und transkristalliner Spannungsrisskorrosion führten zum Versagen von Zugproben der Legierung 7075-T7351 innerhalb der maximalen Prüfdauer von 30 Tagen, insbesondere bei Auslagerung in eine chlorid-nitrathaltige Lösung. [source] Improving the properties of aluminium alloys by retrogression and reageingMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4 2003J. S. RobinsonArticle first published online: 11 APR 200 Abstract Retrogression and reageing heat treatments offer the potential of improved tensile properties in combination with greatly increased resistance to stress corrosion cracking. The potential of this technique is reviewed with respect to the current application in the European and North American Aerospace Industry. To illustrate the performance increase associated with RRA treatments, the stress corrosion cracking performance of the established aerospace plate and forging alloy 7010 has been evaluated using an alternate immersion constant load tensile type test (ECSS-Q-70-37A) Specimens were cut from a large aerospace rectilinear forging and tested in three different tempers, T652, T7452 and a retrogressed and reaged condition (RRA). In the T652 condition the material has been shown to be highly susceptible to intergranular corrosion and stress corrosion cracking. In the T7452 and RRA conditions 7010 showed much improved resistance to SCC but pitting corrosion resulted in failure of some specimens within the 30day requirement of the test standard. [source] Verifizierung zerstörungsfreier Prüfverfahren zur Detektion von Spannstahlschäden an Spannbetonbauteilen mit nachträglichem VerbundBETON- UND STAHLBETONBAU, Issue 8 2005Jürgen Mietz Dr.-Ing. Für die Beurteilung des Gefährdungspotentials bestehender Bauwerke, bei denen im Falle von Spannstahlschäden die Tragfähigkeit nennenswert beeinflußt werden kann, sind zerstörungsfreie Prüfverfahren zur Bewertung des Zustandes der Spannstähle von herausragender Bedeutung. Während des Abrisses der Hohenzollerndammbrücke in Berlin, bei der in früheren Untersuchungen Spannstahlschäden infolge wasserstoffinduzierter Spannungsrißkorrosion festgestellt worden waren, konnten Teile der Stege des Brückenüberbaus entnommen werden. Nach der zerstörungsfreien Untersuchung der dort enthaltenen Spanndrähte mit Hilfe von zwei auf der magnetischen Streufeldmessung sowie einem auf elektromagnetischer Resonanzmessung basierenden Verfahren wurden die Hüllrohre freigelegt und die Spanndrähte inspiziert, um die Ergebnisse der zerstörungsfreien Prüfung im Hinblick auf ihre Zuverlässigkeit zu beurteilen. Die Auswertung zeigt, daß Bereiche mit Brüchen mehrerer Drähte mit den zwei magnetischen Streufeldmeßverfahren detektiert werden können. Verification of Non-Destructive Testing Techniques for Detection of Prestressing Steel Damage at Post-Tensioned Concrete Members For an assessment of the risk potential of existing structures where in the case of prestressing steel damage the load-bearing capacity could be significantly affected non-destructive testing techniques which enable reliable evaluation of the condition of the prestressing steels are of utmost importance. During the demolition of the Hohenzollerndamm bridge in Berlin where damage of prestressing wires due to hydrogen-induced stress corrosion cracking were found in former investigations parts of the girders of the bridge superstructure could be taken out. After non-destructive investigation by means of two testing techniques based on magnetic leakage flux measurement and one technique based on electromagnetic resonance measurement the single wires were inspected in order to verify the non-destructive testing results with respect to their reliability. From the results it can be concluded that areas with fractures of several wires could be detected by the two techniques based on magnetic leakage flux measurement. [source] | ||||||||||