Cathodic protection, abbreviated as CP, is a technique used to prevent corrosion of metal structures and equipment by making them the cathode of an electrochemical cell.  Corrosion occurs when metal is exposed to an electrolyte, such as water or soil, and a flow of electrons occurs between the metal and the electrolyte, resulting in the metal corroding.  By making the metal structure the cathode of an electrochemical cell, the flow of electrons is reversed, and corrosion is prevented.  CP is typically achieved by connecting a sacrificial anode made of a more active metal, such as zinc or magnesium, to the metal structure being protected.  The sacrificial anode corrodes instead of the metal structure, providing cathodic protection.  Another method of cathodic protection is impressed current cathodic protection, which involves using a direct current power source to provide the required current flow to the structure being protected.

CP is commonly used in a variety of industries, including oil and gas, marine, and transportation, to protect metal structures such as pipelines, tanks, and ships from corrosion.  It is a highly effective technique for preventing corrosion, and can extend the life of metal structures significantly.  CP systems require regular monitoring and maintenance to ensure that they continue to function properly over time.  Corrosion engineers and technicians are responsible for designing, installing, and maintaining cathodic protection systems to ensure that metal structures remain protected from corrosion.

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Cathodic Protection Types

Galvanic Anode CP (GACP)  -  Also called sacrifical CP.  Uses a sacrifical anode that corrodes before the material being protected does by an electrochemical reaction (no power source needed).

• Galvanic anode material  -  aluminum, magnesium, and zinc
• Galvanic anode pro
  
  • Easy installation
  • No external power source
  • Require virtually no monitoring or maintenance
• Galvanic anode con
  
  • Limited current, low driving voltage
  • Limited life
  • Limited control, no power source to adjust the power output

Impressed Current CP (ICCP)  -  Uses a sacrificial anode connected to an external DC power source.  DC flows from source to anode, to protected material, to source.

• Impressed current anode material  -  graphite, high silicon cast iron, and mixed metal oxide
• Impressed current anode pro
  
  • Current can be controlled, with no limit of driving voltage
  • Can be remotely controlled
  • Can replace anodes when needed
• Impressed current anode con
  
  • Require regularly monitoring or maintenance
  • Requires power source
  • More monitoring or maintenance means more likely the breakdowns.