Copper-copper sulfate electrode: a copper rod in saturated copper sulfate solution behind a porous plug, with a stable potential of about +316 mV against the standard hydrogen electrode. It is the default reference for buried pipelines and tanks, and criteria such as -850 mV are written against it. The solution must stay saturated with visible blue crystals and the plug kept clean and wet, and readings shift about 0.9 mV per degree C.
All the pipeline numbers are versus CSE, so don't mix them with the silver chloride readings from the dock.
Also heard as
- Cu/CuSO4
- copper sulfate electrode
- copper cell
Related terms
Reference electrode
Electrode with a stable, known potential that serves as the fixed zero for measuring structure potentials.
Half-cell
Field name for the portable reference electrode that CP techs carry to take potential readings.
-850 mV criterion
Steel counts as protected when its potential is -850 mV or more negative against a copper sulfate electrode.
Pipe-to-soil potential
Voltage between a buried pipe and a reference electrode on the soil surface, the basic CP measurement.