What Does Impressed Current Cathodic Protection (ICCP) Mean?
Impressed current cathodic protection (ICCP) is an electrochemical process used to prevent corrosion in metal structures by applying a controlled electrical current to the metal. This process involves the use of an external power source to apply an electrical current to the metal structure, which effectively creates a cathode and thus reduces the corrosion rate of the metal.
Corrosionpedia Explains Impressed Current Cathodic Protection (ICCP)
ICCP is widely used in various industries, such as oil and gas, marine and construction, to protect metal structures from corrosion. For example, in the marine industry, ICCP is used to protect the hulls of ships, offshore platforms, and pipelines from the corrosive effects of seawater. In the oil and gas industry, ICCP is used to protect pipelines and storage tanks from the corrosive effects of the fluids being transported and stored.
The effectiveness of ICCP is based on Faraday's law of electrolysis, which relates the amount of corrosion protection provided by ICCP to the amount of current applied to the metal. The mathematical formula for Faraday's law is as follows:
I = (W × D) / (n × F × Z)
- "I" is the current required for cathodic protection, in amperes.
- "W" is the weight loss due to corrosion, in grams per square meter per day (g/m2/day).
- "D" is the density of the metal, in grams per cubic centimeter (g/cm3).
- "n" is the valence of the metal ion being reduced.
- "F" is Faraday's constant, which is equal to 96,485 coulombs per mole (C/mol).
- "Z" is the number of electrons involved in the reduction reaction.
This formula is used to determine the amount of current required to provide adequate cathodic protection to the metal structure.
Corrosion is a major problem for metal structures in various industries, including oil and gas, marine and infrastructure. Corrosion leads to the degradation of metal structures, which can cause safety hazards, environmental pollution, and economic losses. ICCP is a widely used method for preventing corrosion in these industries.
The principle of ICCP is to create an electrical potential difference between the metal structure to be protected (the cathode) and an inert anode. The potential difference should be negative enough to prevent the electrochemical reaction that causes corrosion. The current that flows from the metal structure to the anode provides a protective layer of electrons that prevents the reaction from occurring. The effectiveness of the ICCP system depends on the current density, which is the amount of current per unit area of the metal surface.
The injected current should be just enough to overcome the original corrosion current and result in an impressed protection current, which flows in the complete circuit. The correct value of protection current can be determined by reference electrodes. Reference electrodes are typically made of either zinc or silver and may be used as the signal source to automatically regulate the value of protection current.
If the current injection is too high, hydroxyl ions will release at a rate causing the the anti-fouling paint to sponge and flake.
The current density required for ICCP depends on several factors, including the type of metal, the environment and the level of corrosion. The required current density can be calculated using the following formula:
CD = (I / A) x K
- "CD" is the current density.
- "I" is the current output of the ICCP system.
- "A" is the surface area of the metal structure.
- "K" is a correction factor that accounts for the specific conditions of the environment.
ICCP is a reliable and effective method for preventing corrosion in metal structures. However, it requires regular monitoring and maintenance to ensure its effectiveness. The reference electrode and anode need to be replaced periodically, and the ICCP system needs to be adjusted to account for changes in the environment.