Pipeline SCC – 1

John A. Beavers, Ph.D., FNACE

External SCC of Pipelines

Pipeline SCC – 2

Pipeline SCC – 3

Pipeline SCC – 4

Environment

Material Stress

Pipeline SCC – 5

SCC

Pipeline 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

Pipeline SCC – 7

Characteristics ofBoth Forms of SCC

The dark area on the fracture surface indicates the extent of the crack before it was broken open

Pipeline SCC – 8

Pipeline SCC – 9

High-pH SCC

Photomicrograph showing high-pH stress corrosion crack.

Pipeline SCC – 10

Near-Neutral-pH SCC

Photomicrograph showing near neutral pH stress corrosion crack

Pipeline SCC – 11

External SCC Integrity Management

Three tools commonly used: Direct assessment Hydrostatic testing In-line Inspection