The site in a corrosion cell where electrons are consumed, usually by reducing dissolved oxygen to hydroxide or water to hydrogen. Current flows from the electrolyte onto the cathode, so the metal there is protected. Cathodic protection works by making the entire structure the cathode of a deliberately built cell, which is also why its surface turns alkaline and, at excessive potentials, evolves hydrogen that can push coatings off.
With enough current on it the whole pipe becomes the cathode and all the corrosion moves to the groundbed.
Also heard as
- cathodic site
Related terms
Anode
Electrode where oxidation happens and metal dissolves; in CP, the hardware installed to discharge current.
Cathodic protection
Shielding buried or submerged steel from corrosion with DC current from sacrificial anodes or a rectifier.
Polarization
Shift of a metal's potential away from its native value caused by current flowing across its surface.
Cathodic disbondment
Loss of coating adhesion around a holiday caused by the alkali and hydrogen that cathodic protection generates.