The voltage a high-impedance meter reads between a buried pipe and a reference electrode set on the ground above it. With the meter positive on the pipe and negative on the copper sulfate electrode, protected steel reads negative and is compared with criteria such as -850 mV. Pipeline operators read it at every test station at least once a year.
Pipe-to-soil potential at the block valve is -1.02 on and -0.91 off, both fine.
Always log which reference electrode you used and where you set it. A reading without that is just a number.
Also heard as
- P/S
- PSP
- structure-to-soil potential
- structure-to-electrolyte potential
Related terms
Reference electrode
Electrode with a stable, known potential that serves as the fixed zero for measuring structure potentials.
Instant-off potential
Structure potential read in the split second after CP current is switched off, free of IR drop.
Test station
Above-ground post or box with wires bonded to a buried structure, used to take CP readings.
-850 mV criterion
Steel counts as protected when its potential is -850 mV or more negative against a copper sulfate electrode.
Low
CP tech shorthand for a potential that is not negative enough to meet the protection criterion.