Stress corrosion cracking (SCC) occurs due to the combination of a susceptible material, a corrosive environment, and sufficient tensile stress. There are various mechanisms of SCC, such as active path dissolution and hydrogen embrittlement, influenced by both metallurgical and environmental factors. To control SCC, strategies include material selection, stress control, and environmental management.

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2. Outline
• Introduction
• The causing of S.C.C.
• Hazards of S.C.C.
‫أشكاله‬
• Factors Affecting Stress Corrosion
• Stress corrosion cracking mechanisms.
• Methods of controlling.

3. 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]
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4. Causes of S.C.C
.
• the occurrence of SCC depends on the simultaneous
achievement of three requirements:
a susceptible material.
an environment that causes SCC for that material.
 sufficient tensile stress to induce SCC. [1]
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5. The environment is either the permanent service environment i.e. sea
water or a temporary one caused by operations such as cleaning of
the system which can leave a residue. [….]
Specific corrosive environment Susceptible metal
𝑁𝐻3∧ammonia compound Copper alloys
Alkalis and nitrates Mild steel
Chlorides and acid chlorides Stainless steel

6. Where do the stresses come from
?
The stresses that cause SCC are either produced as a result of the use
of the component in service or residual stresses introduced during
manufacturing[….] . However, common sources of tensile stresses are:
1. External stresses caused by
Centrifugal forces
Temperature variation
2. Residual stresses due to
Forming
Welding
Rolling
Drawing
Cold or hot bending[….]

7. S.C.C. can proceed in either of two ways:
i. Intergranular stress corrosion cracking.
ii. Transgranular stress corrosion cracking. [….]
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Transgranular Intergranular

8. Factors Affecting Stress Corrosion cracking
1. Metallurgical factors affecting impurities, change of
arrangement, and composition of alloys
2. Environmental factors affecting
some composition (ionic species and their concentration, PH,
dissolved oxygen content), and temperature usually have
substential effects on SCC. [….]

9. Stress corrosion cracking mechanisms
Active Path Dissolution
Film-Induced Cleavage
Hydrogen Embrittlement
 In active path dissolution, the material cracks along the most
corrosion-prone path inside the material. Normally, this path is the
grain boundary where impurities are highly concentrated. The grain
boundary erodes while the surface remains intact. This prevents
early detection of SCC. [2]
 Film-Induced Cleavage produces trans-granular cracks in ductile
materials coated with a brittle film. Ductile Blunting stops the
spread of such cracks beyond 1 m inside the surface. If however
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corrosion has formed this brittle film, cracks form again at the
blunted crack tip and the cycle continues. [2]

10. • Hydrogen Embrittlement starts when hydrogen dissolves in
metals and alloys and makes them brittle by causing loss of
ductility. And hydrogen dissolves easily in metals because it is a
small atom that fits-in conveniently between the atoms of
numerous metals-alloys and diffuses rapidly. [2]
Thus, it is drawn to the regions ahead of cracks or notches that
are under stress. The dissolved hydrogen then assists in the
fracture of the metal, possibly by making cleavage easier or
possibly by assisting in the development of intense local plastic
deformation. [1]

11. Controlling SCC
• There are, consequently, a number of approaches that we can
use to prevent SCC
I. Selection and control of material.
By choosing a material that is not susceptible to SCC in the service environment, and by processing and
fabricating it correctly
.
II. Control of stress
one method of control for external stress is to eliminate that stress, or at least reduce it below the threshold
stress for SCC
.
Residual stresses can be relieved by stress-relief annealing, and this is widely used for carbon steels These
have the advantage of a relatively high threshold stress for most environments , consequently it is relatively
easy to reduce the residual stresses to a low enough level
.
III. Control of environment
The environmental control options consist of adding inhibitors, or isolating the metal from the environment
with coatings. [1]

12. Reference
• [1]: Stress Corrosion Cracking(yellow)
• [2]: Stress Corrosion Cracking (SCC): A Capriciously Insidious
Material Killer
• [3]: http://www.slideshare.net/ElcoCO
• [4]: www.cdcorrosion.com
• [5]: phraspape.cf
• [6]: Packman
• [7]: Research Gate
• [8]: Lambda Technologies
• [9]: NACE International
• [10]: Corrosion Clinic