Literature Review to Chloride Stress Corrosion Cracking
Chloride Stress Corrosion Cracking CLSCC initiates from sites of localised pitting or crevice corrosion. CLSCC propagation occurs when cracks grow more quickly from the pit or crevice than the rate of corrosion.
The initiation of CLSCC has been shown to involve a competition between localised corrosion, which is strongly dependent on chloride concentration but has a weak dependence on temperature, and crack growth which has a strong dependence on temperature but is relatively unaffected by chloride concentration and pH.
It follows from the competition approach that environmental factors, which affect localised corrosion, are also likely to affect the initiation of CLSCC. Furthermore, it also follows that more severe conditions will be required to initiate CLSCC than are needed to sustain crack growth. Recent work has clearly shown that CLSCC crack growth can be sustained at a chloride concentration and temperature significantly below those required to initiate cracking.
There is a large amount of published work on various aspects of CLSCC in austenitic stainless steel. However, no data were found that could be used to predict the time required for crack initiation by localised corrosion in real structures.
Fracture mechanics tests have shown that CLSCC propagation can begin at low stress intensities
in the range 2MPa.m 0.5 to 10MPa.m 0.5. For fabricated structures containing tensile residual stress, the critical depth of localised corrosion to initiate CLSCC would be <1mm.
The rate of crack propagation is strongly dependent on temperature but is relatively unaffected by stress intensity. Rates of CLSCC propagation can vary from 0.6mm.y
-1 at near ambient temperatures to >30mm.yr -1 at temperatures ~100 C. In laboratory tests CLSCC has been observed in samples at temperatures between 25 C and 40 C.
The majority of the reported practical instances of CLSCC have occurred where temperature ≥60 C. However, a significant number of failures below 60 C have also been reported although in these instances there appear to have been other contributory factors which include:
• The use of highly cold worked and/or free-machining grades.
• Iron contamination of the surface.
• The presence of a highly corrosive film containing chloride compounds.
Related References:
1. austenitic stainless steel
2. Stress Corrosion Cracking SCC
3. Chloride Stress Corrosion Cracking (CLSCC)
4. Stress Corrosin Cracking SCC of Duplex Stainless Steel
5. Chloride Stress Corrosion Cracking in Austenitic Stainless Steel
6. Recommendations for Assessing Susceptibility to CLSCC
7. Main Findings on CLSCC in the Reactors
8. Literature Review to Chloride Stress Corrosion Cracking
9. CLSCC Chloride Stress Corrosion Cracking Mechanism
10. Factors Affecting CLSCC Chloride Stress Corrosion Cracking
11. Controlling Chloride Stress Corrosion Cracking
12. Structural Integrity Assessment
13. Non-Destructive Examination NDE
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