Cathode protection system

Cathodic protection explained
Cathodic protection is a method for preventing corrosion on submerged and underground metallic structures.
What is cathodic protection?
Cathodic protection is one of the most effective methods for preventing corrosion on a metal surface.
Cathodic protection is commonly used to protect numerous structures against corrosion, such as ships, offshore floaters, subsea equipment, harbors, pipelines, and tanks; basically, all submerged or buried metal structures.
Basic principles of cathodic protection
The technique is based on converting active areas on a metal surface to passive, in other words making them the cathode of an electrochemical cell
• Sacrificial anode cathodic protection
• Impressed current cathodic protection,
Sacrificial anode cathodic protection
The simplest method to apply cathodic protection is by connecting the metal to be protected with another more easily corroded metal to act as the anode. Zinc, aluminum, and magnesium are the metals commonly used as anodes

The most active metal (which also is the less noble) becomes the anode to the others and sacrifices itself by corroding (giving up metal) to protect the cathode. Hence, the term sacrificial anode.
When is cathodic protection obtained?
Cathodic protection current flow onto any metal will shift its normal potential in the negative direction. Full cathodic protection of steel is obtained by the potential at a certain level.