The Meaning of Cathodic Protection:

The protection of a metal structure from corrosion under water by making it act as an electrical cathode.

Also:

Cathodic protection (CP) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell.

The Cathodic Protection Explained:

Cathodic protection prevents corrosion by converting all of the anodic (active) sites on the metal surface to cathodic (passive) sites by supplying electrical current (or free electrons) from an alternate source.

Usually this takes the form of galvanic anodes, which are more active than steel. This practice is also referred to as a sacrificial system, since the galvanic anodes sacrifice themselves to protect the structural steel or pipeline from corrosion.

Need to Know about Cathodic Protection:

Cathodic Protection

Cathodic Protection System