Cathodic protection is a technique used to protect metal structures or surfaces from corrosion. It involves the use of electrochemical principles to prevent the corrosion of a metal by making it the cathode of an electrochemical cell. By doing so, the metal is protected from the corrosive effects of its environment.

Corrosion occurs when metal surfaces come into contact with an electrolyte, such as water or soil, which contains ions that can react with the metal. This reaction leads to the formation of corrosion products, which weaken the metal and can eventually cause structural failure.

Cathodic protection works by introducing a more easily corroded metal, called a sacrificial anode, into the system. The sacrificial anode is usually made of a metal alloy that has a higher potential to corrode than the protected metal. When the sacrificial anode is connected to the metal to be protected and immersed in the same electrolyte, a galvanic cell is formed.

In the galvanic cell, the sacrificial anode becomes the anode and corrodes preferentially, sacrificing itself to protect the cathode (the metal to be protected). This sacrificial corrosion process prevents the cathode from corroding. The anode material is periodically replaced as it gets consumed over time.