A cathodic protection criterion requiring at least 100 mV of cathodic polarization, shown either by building it up from the native potential or, more often, by switching current off and measuring decay from the instant-off value over hours or days. It suits poorly coated or bare structures where -850 mV is costly to reach, and is avoided where mixed metals, high temperatures, SCC-prone conditions or stray currents make it unreliable.
Can't reach -850 on the old bare main, so shut the rectifier off overnight and prove the 100 mV polarization criterion on decay.
Also heard as
- 100 mV shift
- 100 mV decay
- polarization decay criterion
Related terms
Polarization
Shift of a metal's potential away from its native value caused by current flowing across its surface.
Native potential
Potential of a buried or immersed structure before any cathodic protection current is applied.
Instant-off potential
Structure potential read in the split second after CP current is switched off, free of IR drop.
-850 mV criterion
Steel counts as protected when its potential is -850 mV or more negative against a copper sulfate electrode.