Current Attenuation Along a Pipeline — Distance vs Potential (Diagram #006)
Shows protection/current density decreasing with distance from a CP connection and how coating quality affects attenuation and criteria compliance.
What this visual explains
This diagram shows current attenuation along a pipeline: protective current and polarization generally decrease with distance from a CP current source. Coating condition and circuit resistance control how fast protection attenuates.
Diagram
How to read it
- Near the source: higher available current, stronger polarization.
- Farther away: less available current, weaker polarization (attenuation).
- Coating effect: better coating reduces current demand and changes the profile shape.
- Criteria line: reference line used to visualize “adequate vs inadequate” protection zones.
Field interpretation
- Long spacing between current sources can leave distant segments underprotected.
- Attenuation patterns help prioritize troubleshooting: continuity, coating damage, source location, current output.
- Survey data should be interpreted as a profile (distance context), not isolated readings.
Common mistakes
- Assuming one good test point means the entire segment is protected.
- Ignoring coating condition and assuming attenuation is purely “distance.”
- Comparing readings without accounting for interruption state (ON vs OFF) and gradient effects.
CP 3 relevance
Attenuation shows up in CP 3 calculations and troubleshooting scenarios (spacing, resistance, coating, current demand). This visual supports interpreting surveys and understanding why “far end” issues occur.