Native Potential

Native potential is the natural structure-to-electrolyte potential of a structure before CP is applied or after CP influence has been removed long enough for depolarization.

Quick Definition

Native potential is the potential of a structure in its unprotected or sufficiently depolarized condition.

Why This Term Matters

Native potential can be used as a baseline for evaluating the cathodic shift caused by CP. It is important in current requirement testing, commissioning, depolarization surveys, and polarization calculations.

A reading should not be called native if active CP current, stray current, or other electrical influence is still affecting the structure.

Core Concept

Baseline condition

Native potential is intended to represent the structure before CP influence.

Depolarized condition

In existing CP systems, a depolarized potential may be used when a true pre-CP native value is unavailable.

Environmental dependence

Native potential varies with material, electrolyte, oxygen, moisture, temperature, corrosion activity, and surface condition.

Use in calculations

Native or depolarized potential may be compared with a polarized potential to calculate polarization shift.

Common Mistakes

Calling a CP-influenced reading native.
Why it is wrong: Native potential should represent an unprotected or sufficiently depolarized condition.
Assuming native potential is constant everywhere.
Why it is wrong: Electrolyte and surface conditions vary by location.
Using native data from one location for another location.
Why it is wrong: Polarization comparisons must represent the same structure condition or test point.

Field Example

Before a temporary CP current requirement test, a structure reads −620 mV_CSE. After temporary CP is applied, the instant-off potential is −760 mV_CSE. The cathodic shift is 140 mV if the readings represent valid comparable conditions.