There are two forms of stress corrosion cracking (SCC) that can affect pipelines: high-pH (classical) SCC and near-neutral-pH (low-pH) SCC. Both forms refer to the pH of the electrolyte beneath disbonded coatings, not the soil pH. Pipeline operators use three main integrity management tools to assess pipelines for external SCC: direct assessment, hydrostatic testing, and in-line inspection.

1. External SCC of Pipelines John A. Beavers, Ph.D., FNACE

2. Pipeline SCC –

3. Pipeline SCC –

4. Pipeline SCC –

5. Environment Material Stress Pipeline SCC – SCC

6. Two Forms of SCC High-pH (Classical) SCC Near-Neutral-pH (Low-pH) SCC pH refers to electrolyte beneath disbonded coating, not soil pH

7. Characteristics of Both Forms of SCC

8. The dark area on the fracture surface indicates the extent of the crack before it was broken open Pipeline SCC –

9. High-pH SCC Photomicrograph showing high-pH stress corrosion crack.

10. Near-Neutral-pH SCC Photomicrograph showing near neutral pH stress corrosion crack

11. External SCC Integrity Management Three tools commonly used: Direct assessment Hydrostatic testing In-line Inspection