What is cathodic protection?
Cathodic protection (CP) is a technique used to control the corrosion of a metal substance in various applications. Some common areas which apply this science are fuel tanks, pier pilings, ships, offshore oil platforms and casings, metal reinforcement bars for concrete structures, as well as pipelines.
Cathodic Protection (CP)
To simplify cathodic protection, assume you have a metal pipeline, and you need to protect it against corrosion. We supplement pipelines with CP after being protected with an anti-corrosion system (coating or wrap), such as Trenton Wax Tape, as the primary form of corrosion protection. Otherwise, the cathodic protection required to combat corrosion for an uncoated pipeline is excessive.
The first step in cathodic protection is to take the metal you are trying to protect (pipeline) and turn it into a cathode. A pipe usually is anodic; it contains positively charged particles. By supplying an electric current, the pipe becomes passive or cathodic. The science reveals that as long as the flow is arriving at the cathode (pipeline) faster than oxygen is, then corrosion will be prevented or significantly slowed.
Pipelines commonly use Impressed Current Cathodic Protection (ICCP) which uses a rectifier along with anodes buried in the ground. The rectifier (a DC power source) supplies electrons to the system stopping corrosion of the pipeline, and since the anodes do not surrender many electrons, they do not corrode much either.
Sometimes it is more economical to use a galvanic anode system in which the anodes (Magnesium, Zinc or Aluminum) are the electron source and are sacrificed and corrode over the steel pipeline.
The video below offers a simple representation of ICCP.