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| Corrosion & Environmental Degradation |
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| Stress
Corrosion
· In a corrosive environment, failure due to crack propagation occurs at a shorter time as the applied tensile stress is increased. (See the top Diagram) · The crack propagation in this stress-corrosion environment shows non-ductile (brittle) behavior even if the metal is ductile. The crack tip is a stress concentrator, and rapid dissolution of the metal in this region prevents the crack tip from blunting due to the plastic deformation. · Crack propagation is frequently trans-granular in the presence of Cl-, NO3-, and OH- ions. · Shown is a stress-corrosion crack the neck region of an austenitic-ferritic steel tested in uniaxial tension. The sample had been in a boiling 30% MgCl2 solution and the strain rate was 2 x 10 -6 /sec. The crack is seen to be trans- granular in the austenitic phase (dark). |
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| Chart
from: Van Vlack,
"Elements of Materials Science and Engineering," Addison Wesley (1985) |
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