Theory 16/Pipeline Engineering
Corrosion Is a Protection Ratio
The claim
External pipeline corrosion occurs where the ratio of cathodic protection current to coating defect area falls below a threshold, so a well-protected pipe can corrode at a small defect.
01Mechanism
Protection requires enough current to polarise the exposed steel; at a defect, the current density depends on how much protected area surrounds it.
02Predictions
- P1Corrosion should cluster at low-ratio defects.
- P2Pipe potential alone should mispredict.
03Refutation
Corrosion tracking potential would remove the geometry.