Stress corrosion cracking environments promoting

Early use of the test was in providing data whereby the effects of such variables as alloy composition and structure or inhibitive additions to cracking environments could be compared, and also for promoting stress-corrosion cracking in combinations of alloy and environment that could not be caused to fail in the laboratory under conditions of constant load or... 

Tabic 9.4 Environments known to promote stress-corrosion cracking in certain engineering... 

Stress-Corrosion Cracking. The conditions for SCC to occur are (i) a crack-promoting environment (ii) the susceptibility of material to SCC (iii) tensile stresses must exceed the threshold value. SCC is distinguished by the fact that the stress corrosion faces suffer very low corrosion, even in solutions that cause some damage to the free surfaces. As an example is the SCC of stainless steel at 200°C in a caustic solution or in aerated chloride solution where almost no traces of dissolution are visible on the crack faces (Figure 6.53).84,95 For example, SCC of metals has been by far the most prevalent... 

From the ASTM definition, stress corrosion cracking is the simultaneous action of a corrosive environment and a sustained tensile stress promoting rupture" [54]. Both SCC and deallo)dng often occur in the same environment. By the 1940s, deaUoying was considered to be involved in the initiation of SCC [57]. 

One of the most serious failures that can occur in service is the phenomenon known as stress corrosion cracking (SCC). SCC appears in particrrlar crack-promoting enviromnents when the metal or the alloy is subjected to a terrsile stress above a specific minimum threshold value. The joint action of stress and the aggressive environment produces ductility losses, leading to brittle failtrre of a normally ductile material like aluminum. 

Stress corrosion is an interaction of sustained tension stress and corrosive attack causing cracking that can result in premature brittle failure of a ductile material. Before stress corrosion can occur, there must be the proper combination of a chemical environment and metallurgical condition of the material. Failures of this type have been identified with certain alloy systems of practically all metals, and in most instances the failures have been shown to be associated with electrochemical activity. In aluminum alloys, stress corrosion can be promoted by a film of moisture on the surface of... 

Mechanical Facton, Environments that promote metal dissolution can be considered more damaging if stresses are involved (see the discussion on stress-corrosion cracking in Chapter 7). In such circumstances, materials can fail catastrophically and unexpectedly. Safety and health can be significantly affected. 

The environment also plays a role in some environments brittle crack failure is strongly promoted. For example, detergents such as synthetic soaps can decrease the time to brittle failure of PE by a factor between 10 and 50 (see Figure 7.21). This phenomenon is known as stress corrosion or environmental stress cracking (ESC) (see further 8.5). 

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