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Cathodic Protection

Cathodic Protection, Corrosion

cathodic protection banner 8Cathodic 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.

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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.

Cathodic Protection Anode Types

Galvanic (Sacrificial) Anode   -  Galvanic (or sacrificial) anodes are a type of cathodic protection system used to prevent corrosion in metal structures, such as pipelines, ship hulls, and storage tanks.  These anodes are made from metals that are more electrochemically active than the structure they protect, typically zinc, magnesium, or aluminum alloys.  When connected to the structure in an electrolyte like soil or water, the anode corrodes preferentially, sacrificing itself by releasing electrons to the protected structure (the cathode).
Impressed Current Anode  -  Unlike sacrificial anodes, impressed current anodes are made from relatively inert, durable materials such as mixed metal oxide (MMO) coated titanium, high-silicon cast iron, graphite, or platinized titanium.  These anodes are connected to an external power source, typically a rectifier, which supplies a controlled electrical current to drive electrons through the electrolyte (soil, water, or concrete) to the protected structure, keeping it cathodic and corrosion-free.  

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