The free-corrosion potential of a structure measured against a reference electrode with no CP current flowing, typically somewhere around -500 to -800 mV CSE for steel in soil. It is the baseline for the 100 mV polarization criterion and for spotting galvanic couples and interference. Native readings are taken at construction, before rectifiers are energized or anodes connected, and kept in the test station history.
Native potential at the new station was -620, so we need at least -720 polarized to claim 100 mV.
Also heard as
- corrosion potential
- free-corrosion potential
- open circuit potential
- OCP
- static potential
Related terms
100 mV polarization criterion
CP criterion met when a structure is polarized at least 100 mV more negative than its native potential.
Pipe-to-soil potential
Voltage between a buried pipe and a reference electrode on the soil surface, the basic CP measurement.
Polarization
Shift of a metal's potential away from its native value caused by current flowing across its surface.
Reference electrode
Electrode with a stable, known potential that serves as the fixed zero for measuring structure potentials.