Chloride Stress Corrosion Cracking | Materials And Corrosion Control
| Damage Mechanism | Chloride Stress Corrosion Cracking |
| Damage Description | Surface initiated cracks caused by environmental cracking of 300 SS under the combined action of tensile stress, temperature and an aqueous chloride environment. The presence of dissolved oxygen increases the cracking susceptibility.
Branched, mostly transgranular cracks with a crazed or spider-web and brittle appearance. Trace levels of chloride can concentrate even at very low levels. This can occur in reboiler tubes, rich-lean exchangers and the reclaimer and if U-bends are not stress relieved or solution annealed. |
| Affected Materials | 300 Series austenitic stainless steels ≥ 60°C
Duplex stainless steels ≥ 130°C, depending on the grade and heat treatment. |
| Control Methodology | Use more resistant materials (not susceptible to Cl-SCC)
Maintain chloride levels < 500 ppmw in the amine solution Avoid designs that allow stagnant areas where chlorides can concentrate or deposit. Slope to drain with no pockets If problematic, replace socket welds with resistant material When hydro testing austenitic stainless steel, use low chloride content water. Follow SAES-A-007 |
| Monitoring Techniques | Shear wave UT (or Time of Flight Diffraction) around butt welds during the T&I PT of exposed surfaces |
| Inspection Frequency | Shear wave 10% of butt welds during each T&I at selected high risk locations |
| KPIs | Chloride level exceedances
# of failures(cracks) % of inspections conducted |
| Reference Resources (Standards/GIs/BPs) | API RP 571 (DM #23) SAES-A-007 SAES-L-133 |
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