100 mV Polarization Decay Criterion
Checks polarisation by formation and by decay against the 100 mV criterion, beside the -0.850 V criterion.
Example
You enter
- ON potential (V, negative) -1.05
- Instant-off potential (V, negative) -0.78
- Native potential (V, negative) -0.65
- Depolarised potential (V, negative) -0.67
- Absolute criterion (V, e.g. -0.850) -0.85
- Polarisation criterion (mV) 100
You get
- IR drop in the ON reading 270 mV of soil, not steel
- Polarisation by formation 130
- Polarisation by decay 110
- Absolute margin mv -70
- Decay measured from ON -- the error 380 mV against a true 110 mV, 3.5 times over
- Decay overstatement ratio 3.45455
Details, formula, and sources
The worked line fails -0.850 by 70 mV and is properly protected under 100 mV. Measuring decay from the ON potential overstates it 3.5 times and certifies an unprotected line.
formation = native minus instant-off; decay = depolarised minus instant-off; both against 100 mV, always from the instant-off; plus -0.850 V on the instant-off.
NACE SP0169 (now AMPP) and the CP designer govern.
The criteria are in NACE SP0169.
Estimate. AHJ and licensed professional govern.
Field names used by the API: on_potential_v, instant_off_potential_v, native_potential_v, depolarized_potential_v, criterion_v, polarization_criterion_mv, ir_drop_mv, formation_mv, decay_mv, absolute_margin_mv, decay_from_on_mv, decay_overstatement_ratio
- Reference decay and formation are always measured from the instant-off potentialNACE SP0169
- Criterion choice which criterion applies depends on the structure and the standardCP designer