A technique that stops external corrosion of buried or submerged metal by pushing DC current onto it from anodes through the electrolyte, shifting its potential negative until anodic sites stop dissolving. Current comes from sacrificial anodes or from rectifiers driving impressed-current groundbeds. CP works as a team with coatings: the coating does most of the work and CP protects the holidays. Pipelines, tank bottoms, hulls, offshore jackets and reinforced concrete all use it.
Cathodic protection on the gathering system is down, the rectifier at station 4 tripped in the storm.
Bare pipe can take hundreds of times more current than well-coated pipe, so coating breakdown usually shows first as a rectifier that keeps needing more output.
Also heard as
- CP
Related terms
Sacrificial anode
Block of a more active metal such as magnesium, zinc or aluminum that corrodes to protect connected steel.
ICCP
Impressed current cathodic protection: CP powered by a rectifier pushing current through long-life anodes.
Rectifier
Transformer-rectifier unit that turns AC power into adjustable DC current for an impressed current CP system.
-850 mV criterion
Steel counts as protected when its potential is -850 mV or more negative against a copper sulfate electrode.
Holiday
Pinhole, void or bare spot in a coating that leaves the metal underneath exposed.