Field Failure and Laboratory Test. Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Skudai, 8. Johor, Malaysia. 2Department of Refrigeration and Air Conditioning, Politeknik Negeri Bandung, Bandung 4. Indonesia. 3Faculty of Maritime Studies and Marine Science, University Malaysia Terengganu, 2.
SUBJECT: Corrossion problems associated with stainless steel 4-1. The rotating equipment business uses a great deal of 300 series stainless steel, and as a result we. 1.0 Introduction Stress corrosion cracking is cracking due to a process involving conjoint corrosion and straining of a metal due to residual or applied stresses.1. Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected sudden failure of normally ductile metals. Controlling Stress Corrosion Cracking (SCC) In order for SCC to occur, we require a susceptible material, an environment that will cause cracking of that material and.
Kuala Terengganu, Malaysia. Copyright . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Through an investigation of the field failure analysis and laboratory experiment, a study on (stress corrosion cracking) SCC behavior of steel and aluminum was performed. All samples were extracted from known operating conditions from the field failures. Similar but accelerated laboratory test was subsequently conducted in such a way as to mimic the field failures. The crack depth and behavior of the SCC were then analyzed after the laboratory test and the mechanism of stress corrosion cracking was studied.
The results show that for the same given stress relative to ultimate tensile strength, the susceptibility to SCC is greatly influenced by heat treatment. Furthermore, it was also concluded that when expressed relative to the (ultimate tensile strength) UTS, aluminum has similar level of SCC susceptibility to that of steel, although with respect to the same absolute value of applied stress, aluminum is more susceptible to SCC in sodium hydroxide environment than steel. Introduction. Engineers in the field often assume that within the same group of materials, for example, group of ferrous or group of nonferrous, only the chemical composition is relevant when selecting materials for corrosive environments. Not so many of them consider the effect of heat treatment, let alone the microstructure. On the other hand, it is widely known that petroleum and natural gas systems can be contaminated with solutions that are sometimes very aggressive to engineering materials, such as steels and aluminums, which are used in the transport and processing of petroleum products. It has been reported from decades ago that up to a quarter of equipment failures in the petroleum refining industry are in some way associated with (stress corrosion cracking) SCC and hydrogen damage . Although SCC of austenitic steel is the most common, steel with other microstructures can also undergo SCC.
- CORROSION FUNDAMENTALS: DEFINITION OF CORROSION Corrosion can be defined as the destruction or deterioration of a material through reaction with its environment.
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Therefore, SCC is not only unique to austenitic steel but also problematical in ferrite- pearlite and martensitic steels and aluminum alloys as well. This also has been known for long time . Publications on the studies of SCC on ferrite- pearlite in the environment of Na.
OH were started quite a while ago, and it remains actively studied up to now . The SCC behavior is highly dependant on the microstructure. However, they focused on the depth of the crack and did not analyze a morphology of the crack. Similarly, SCC failure is also reported in aluminum and its derivative alloys .
It is also commonly understood that aluminum alloys that contain considerable amounts of soluble alloying elements, especially copper, magnesium, silicon, and zinc, are susceptible to SCC. They can fail by cracking along grain boundaries when simultaneously exposed to specific environments and sufficient magnitude of stresses. Well- known environments that can trigger SCC include but are not limited to water vapor, aqueous solutions, acids (such as acetic acid), organic liquids, liquid metals, and salt solutions. Stresses sufficient for crack initiation and crack propagation can be far below the stresses required for gross yielding. Unlike for high- strength materials such as steels, papers discussing about SCC of aluminum are rather scarce .
While majority of papers focus on the chemical composition of aluminum alloys in various corrosive solutions, few of them focus on the effect of heat treatments or microstructures . The environment used was sodium hydroxide. The laboratory test was an accelerated version of what happens in the field. Case Study Figure 1 shows metallography of the samples from the field failures of both aluminum and the steel samples failed in similar environments. Although the environments in which all actual parts used were similar, the degree of the stress corrosion cracking is clearly different. For the steel, austenite was the most sensitive to SCC, followed by martensite, and finally ferrite- pearlite.
Return to Failure Analysis Case Histories. Chloride Stress Corrosion Cracking of Buried Stainless Steel Pipeline: ENVIRONMENT: Eastern U.S.
All the samples were obtained from an oil company. While further detailed information is confidential, the environments in which they were being used contained some sodium hydroxide (Na. OH). All the pipes had been in service for more than 8 years. Further discussion only on the steel part of this project has been reported along with the basic general mechanism of the SCC .
CTL- Chloride Stress Corrosion Cracking of buried Stainless Steel Pipeline. The material of construction must be exposed to tensile stresses. Thermal stresses due to varying operating temperatures, ineffective expansion bellows, or residual stresses from welding have all been found capable of promoting stress corrosion cracking. This pipeline showed evidence of exposure to all three sources of stresses.