Prevent Stress Corrosion Cracking Research Articles

Stress Corrosion Cracking in Fibreglass Composite Structures - A Case Study

One failure mechanism experienced by fibreglass composite structures is stress corrosion cracking, which occurs in structures under load in a corrosive environment. Over time, stress corrosion cracking attacks the glass fibres, which weakens the structure and can lead to premature failure. Stress corrosion cracking failure is characterized by flat fracture surfaces perpendicular to the fibres at both the macroscopic and microscopic levels. Prevention of stress corrosion cracking includes proper selection of fibre and resin, and use of a protective layer between the glass fibres and the environment. Fibreglass structures that have failed due to stress corrosion cracking include chemical tanks, sewer pipe and pressure vessels. This paper describes the phenomenon of stress corrosion cracking in fibreglass composite structures. It also presents, as a case study, the investigation of the failure of a fibreglass overwrapped compressed air cylinder, used in a self-contained breathing apparatus. The failure was attributed to stress corrosion cracking following exposure to a highly acidic cleaning fluid. The cause of the failure was determined based on the results of fractography, chemical analysis, and stress corrosion tests performed on samples of the accident cylinder.

Stress Corrosion Cracking in Fibreglass Composite Structures - A Case Study

One failure mechanism experienced by fibreglass composite structures is stress corrosion cracking, which occurs in structures under load in a corrosive environment. Over time, stress corrosion cracking attacks the glass fibres, which weakens the structure and can lead to premature failure. Stress corrosion cracking failure is characterized by flat fracture surfaces perpendicular to the fibres at both the macroscopic and microscopic levels. Prevention of stress corrosion cracking includes proper selection of fibre and resin, and use of a protective layer between the glass fibres and the environment. Fibreglass structures that have failed due to stress corrosion cracking include chemical tanks, sewer pipe and pressure vessels. This paper describes the phenomenon of stress corrosion cracking in fibreglass composite structures. It also presents, as a case study, the investigation of the failure of a fibreglass overwrapped compressed air cylinder, used in a self-contained breathing apparatus. The failure was attributed to stress corrosion cracking following exposure to a highly acidic cleaning fluid. The cause of the failure was determined based on the results of fractography, chemical analysis, and stress corrosion tests performed on samples of the accident cylinder.

原子炉内リフレッシュ技術の開発

Japan has fifty nuclear power plants in operation and some of them has been operated more than twenty five years. It becomes more important to develop maintenance technologies to prevent unscheduled outage. We have developed wet shot peening system to change tensile stress to compressive stress around the weld preventing stress corrosion cracking (SCC).Together with the stress improvement technology, we have developed multipurpose remote handling equipment to execute the tasks required in a core area and an annulus area.

Measures for reducing SCC in anhydrous ammonia storage tanks

AbstractThe results from four research projects on ammonia stress corrosion cracking (SCC) are provided, including the effect of oxygen and water in the ammonia, prevention of SCC with electrochemical methods, crack growth rate studies, and behavior of welds. Practical recommendations are given for construction, inspection, repair, commissioning, and operation of ammonia storage tanks.

高温ＮａＯＨ‐Ｎａ２Ｓ水溶液中のステンレス鋼の応力腐食割れ挙動と最適材料

The selection of stainless steels to prevent stress corrosion cracking (SCC) in hot sodium hydroxide solution containing small amount of sodium sulfide was determined by order of the critical temperature of SCC occurrence and by the electrochemical behaviour. SCC susceptibility of stainless steels might be governed by chemical compositions, the nickel and chromium content.It was possible to presume that SUS 310S had enough resistance to use in industry.In comparison with SCC behaviour of SUS304L conducted with various SCC test methods, the detecting SCC was able to reproduce with not only the Lehigh restraint test but also the slow strain rate tensile tests at the same test conditions as in the U-bend test.

The achilles expert system on corrosion and protection: Consultations on aspects of stress corrosion cracking

The ACHILLES expert system provides broad ranging advice on corrosion, protection, material selection and failure diagnosis. It contains modules dealing with nine aspects of corrosion, one of which is stress corrosion cracking (SCC). Each module was based on information provided by an expert in the form of a document or “resource digest”. The “Aspects of Stress Corrosion Cracking” module deals with the following topics: introduction to SCC, diagnosis, detection, monitoring and prevention of SCC, SCC of steels in various environments and SCC in specific plant items. Two example consultations are presented.

Use of the mechanical stress improvement process to mitigate stress corrosion cracking in BWR piping systems

Abstract The mechanical stress improvement process (MSIP) has been extensively applied to prevent stress corrosion cracking in BWR plants. MSIP removes residual tensile stresses from weldments, thus preventing the initiation of cracks and retarding the growth of pre-existing flaws in piping systems. The process involves a slight permanent contraction of the pipe on one side of the weldment. The resulting plastic flow redistributes the residual as-welded stresses and generates beneficial compressive stresses at the inner pipe surface in the region of the weldment including the weld metal and heat-affected zones. MSIP imposes only monotonic compressive plastic strains and does not require severe temperature gradients. Hence, use of MSIP is particularly advisable for weldments which include geometrical or material discontinuities such as nozzle-to-safe-end welds. Moreover, the process can be applied to the piping system either filled with water or empty. MSIP is accepted by NUREG 0313 as a stress Improvement (SI) process for mitigation of IGSCC in BWR plants. To date it has been applied to 532 welds in 12 BWR plants in the United States and abroad. MSIP has been used to improve 157 nozzle weldments ranging from 4′′ to 28′′ diameter. The process has also been applied to weldments with pre-existing cracks. The basic concept, results of analyses and tests, and application of MSIP are described herein.

化学プラントにおける応力腐食割れ事例とその対策について

Stress corrosion cracking is the most numerous and the most serious problem in the corrosion problems in chemical plants. So the prevention of stress corrosion cracking is the most important theme. In this paper, the following examples and their preventive methods are given; SCC of austenitic stainless steel in chloride solution, caustic embrittlement of carbon steel in vertical boiler, SCC of Type 304 in electrolysis plant and SCC of Hastelloy alloy.

The amount of chlorine contamination for prevention of stress corrosion cracking in sensitized type 304 stainless steel

Stress corrosion cracking (S.C.C.) of sensitized Type 304 stainless steel was investigated under conditions of chloride contamination with varying tensile stress level and relative humidity as an environmental condition. The results obtained were summarized and the allowable chlorine concentration of the contaminant for the prevention of S.C.C. was determined. The effect of relative humidity on S.C.C. was also discussed.

溶接後水冷法によるオーステナイト系ステンレス鋼の応力腐食割れ防止 -応力腐食割れにおける溶接残留二軸応力の評価法-

溶接後水冷法によるオーステナイト系ステンレス鋼の応力腐食割れ防止 -応力腐食割れにおける溶接残留二軸応力の評価法-

残留応力管理による現場装置の応力腐食割れ防止

残留応力管理による現場装置の応力腐食割れ防止

Use of electrochemical techniques for corrosion prevention and control in the process industries

Electrochemical techniques are described of direct use to chemical processors for optimum material selection in designing and maintaining new plants as well as corrosion monitoring and control in operating existing plants. Reference is made to the three corrosion forms most responsible for failures in chemical equipment, i.e.: general corrosion, localised corrosion, and stress‐corrosion cracking. Practical examples are given of successful industrial application of electrochemical methods: 1) for controlling active corrosion of a stainless alloy in pressure reactors operated with hot sulphuric acid solution and 2) for preventing stress corrosion cracking of a low‐alloy steel in a pressure absorption tower operated with hot alkali carbonate solution.

Shot peening to prevent the corrosion cracking of austenitic stainless steels

Rockwell International and Metal Improvement Company have conducted a joint test program to develop shot peening as a technique for preventing corrosion cracking in austenitic stainless steels. Initial laboratory-scale tests demonstrated the feasibility of preventing stress corrosion cracking by shot peening to impose compressive stresses on the surface of the work pieces. Conventional U-bend test specimens, when peened, survived 1000 h tests in the boiling 42 pct magnesium chloride stress corrosion test. Unpeened reference specimens commonly fractured within one or two hours in this test. Component tests were conducted to demonstrate the practicality of the peening process for sizes and shapes that typify components in a reactor piping system. Pipe sections and cold worked, hexagonal tubes were tested. In all components, unpeened sections developed stress corrosion cracks within a few hours in the magnesium chloride test; in contrast, the shot peened surfaces survived hundreds of hours. It was discovered at Rockwell International that intergranular corrosion can be prevented in austenitic stainless steels by severe shot peening prior to exposure to sensitizing temperatures. For this purpose, the surfaces must be severely cold worked by the shot peening to break up surface grains and grain boundaries. Two nondestructive testing techniques show promise as methods for measuring the stresses or cold work imparted on the surface of the work piece by peening. In one method, eddy currents are used to measure differences in electrical properties induced by cold working of metals. Another is a magnetic technique which measures the changes in magnetic properties due to the transformation of austenite to ferrite by cold working.

Stress Corrosion Cracking of Mild and Low Alloy Steels in CO-CO2-H2O Environments

Abstract This paper is related to the new stress corrosion cracking phenomenon of mild and low alloy steels in a CO/CO2 environment. The incidents of cracking are described and these were reproduced by laboratory tests. The results obtained are as follows: (1) No stress corrosion cracking of mild steel was found to occur in water containing just CO or CO2. (2) The transgranular stress corrosion cracking occurred only in CO/CO2 environment with water. (3) Stress corrosion cracking occurred in a wide range of CO/CO2 ratios in water. (4) The susceptibility to stress corrosion cracking of mild steel decreases with increasing temperature. (5) No stress corrosion cracking was found to occur on 18Cr-10Ni stainless steel. (6) From the study of electrochemical measurements, the mechanism has been proposed that this form of cracking is stress corrosion cracking rather than hydrogen embrittlement. (7) Prevention of stress corrosion cracking in these environments is discussed.

Prevention of Stress-Corrosion Cracking of Kovar Material

Prevention of Stress-Corrosion Cracking of Kovar Material

オーステナイト系不透鋼の応力腐食割れに関する研究(第8報)

The stress corrosion cracking of austenitic stainless steels occurs not only due to the welding stress, but also due to the working process such as pressing and bending. Especially there are many problems, when the cold-worked material is welded, that is to say, the sensitivity of the material for stress corrosion cracking will be changed by plastic deformation, while at the same time, the value of welding stress in the cold worked material is assumed to become higher.In this reportt authors discussed the cold work dependence of the sensitivity for stress corrosion cracking in two kinds of austenitic stainless steels such as SUS 27 and SUS 32 in the boiling solution of 42% MgCl2.In the material like SUS 27 which transforms to quasi-martensite under cold working, the resistance to stress corrosion cracking grows through cold working. It is estimated that the quasi-martensite acts as an anode spot in the corrodent, consequently the type of corrosion changes into general corrosion.Next, it is confirmed by experiment that the resistance to stress corrosion cracking of cold worked SUS 27 drops through reheating to over 500°C. This is due to the fact that the martensitic structure is resolved.On the other hand, the material like SUS 32 shows no change in the time-to-fracture of stress corrosion, even though it has been cold worked. In this material, no martensitic transformation has been observed after the cold working process.Next, authors measured. the welding stress of the pre-tensioned plates. The tensile residual stress along the weld line reachers a maximum at about 10 mm distance from weld line, and it is almost the same value as the increased yield stress of the cold worked material.The initiation of cracks in such material is earlier than that in the material without the cold working process. This fact can be observed in both SUS 27 and SUS 32.From this experiment, it may be said that even though the cold work is confirmed, in laboratory, to be good for stress corrosion cracking, this fact cannot be applied to welded structures for prevention of stress corrosion cracking.

アルミニウムメッキによる18-8オーステナイト系ステンレス鋼の応力腐食割レ防止について

アルミニウムメッキによる18-8オーステナイト系ステンレス鋼の応力腐食割レ防止について

オーステナイト系不銹鋼の応力腐食割れに関する研究(第5報)

We discussed the relation between corrosion potential and the so called "induction period" of austenitic stainless steels which.were subjected to stress corrosion cracking test under cathodic or anodic electrolysis.In the case of cathodic electrolysis, the corrosion potential of the test piece was lowered. Consequently, it took longer time until the corrosion potential reached the necessary value for initiation of crack described in the previous reports. Therefore, the induction period was also lengthened. .When the current density of cathodic electrolysis increased sufficiently, no stress corrosion crack occurred during the test time. In this case, the corrosion potential did not reach the necessary value for initiation of crack.This is the mechanism of prevention of stress corrosion cracking by the cathodic electrolysis.Next, we applied the cathodic current to the restrained welded plate being under stress corrosion test, and proved that the cathodic electrolysis would be effective to prevent stress corrosion cracking.Moreover, we made clear that the propagation of stress corrosion crack could also be controlled by the corrosion potential of test piece.

Stress Corrosion Cracking off Ti and Zr in HCl-Methanol Solutions

Abstract It was discovered by the authors that Ti is easily attacked by stress corrosion cracking in methanol containing HCl. This is a report on a study to assess quantitatively stress corrosion cracking of Ti in alcohol solutions. At the same time stress corrosion cracking of Zr was studied because of its similarity in chemical behavior to Ti. Stress corrosion cracking of Ti occurs in methanol solutions containing HCl or H2SO4 and that of Zr is observed in methanol containing HCl or H2SO4 or HCOOH and in ethanol containing HCl. In HCl-alcohol solutions it is observed also that the larger the molecular weight of the alcohol, the longer life the metals have. Addition of water to HCl-methanol solution prevents stress corrosion cracking of Ti and Zr. Critical concentration of water in 0.4 percent HCl-methanol solution is about 1.5 percent for Ti and about 3 percent for Zr. To prevent stress corrosion cracking by stress relief, annealing temperatures should be higher than 500 C (932 F) for Ti and 450 C (842 F) for Zr.

Studies on Stress Relieving Methods for Welded Joints of Stainless Clad Steel : 1st Report, The Mechanism of Residual stresses Due to Welding

In this paper, the method of plastic stress analysis is applied to analyze the residual stress in the stainless steel weldings of stainless clad steel. As a result, the relation between welding conditions and the amount of residual stress was obtained, and the validity of these results was confirmed experimentally. As a result, it was recognized that large tensile stress occurs on the stainless steel welded surface, and the need was stated for providing stress relief to the welded parts of stainless steel in order to prevent stress corrosion cracking when they are used in the atmosphere in which such cracking is likely to occur. It was also suggested that this method of analysis would be of use in the analysis of contraction and deformation due to welding.