Impressed Current Cathodic Protection

Impressed Current Cathodic Protection

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What is the difference between a Sacrificial Anode and Impressed Current Cathodic Protection system? Learn about when an Impressed Current Cathodic Protection system is needed and the types of structures it can protect from corrosion.

Scene #1:

Impressed Current Cathodic Protection

Scene #2:

In Sacrificial Anode Cathodic Protection systems, galvanic anodes are connected to a metallic structure and supply DC current to it.
The structures that receive current are cathodically protected from corrosion.
The galvanic anodes, on the other hand, corrode as they discharge current.
As the size of the structure grows, more galvanic anodes are required to supply enough current to protect the structure.

Scene #3:

In large applications, many galvanic anodes are needed to provide the required current.
In these cases, Sacrificial Anode Cathodic Protection systems are not cost-effective.
Some examples of larger applications are bridges, skyscrapers, large ships, dams and pipelines.

Scene #4:

To mitigate corrosion in these systems, we need a source of more DC current.
The Solution?
Impressed Current Cathodic Protection.

Scene #5:

In an Impressed Current Cathodic Protection System,
  • We replace galvanic anodes with non-consumable, inert, impressed current anodes.
  • We use a rectifier to supply DC current.

Scene #6:

The rectifier allows us to supply enough DC current to protect the structure by adjusting the rectifier output voltage.
Too little current, and the structure is vulnerable to the corrosion we want to mitigate.
Too much current, and the structure is vulnerable to overprotection.

Scene #7:

Overprotection is not just a matter of wasted power.
It can cause coating separation, structure brittleness, and surface deposits (in marine environments).
It can even cause alkaline conditions which promote the corrosion we’re trying to prevent.
Therefore, not only is proper design important, but also close monitoring of the system.

Scene #8:

Reference electrodes are often permanently installed as a part of the Impressed Current Cathodic Protection system.
Reference electrodes provide important feedback about how well the system is performing.
  • They are used to tune the power settings on the rectifier.
  • They are used for periodic monitoring throughout the life of the structure.
  • They help us determine if the system is operating correctly.

Scene #9:

Both Sacrificial Anode and Impressed Current Cathodic Protection systems are effective methods of mitigating corrosion.

Scene #10:

Sacrificial Anode Cathodic Protection systems are typically used for applications where the current requirements are small.
They are also suited for structures that are buried or placed in soil with low resistivity.
Some of these applications could be small storage tanks, small boats, ballast tanks and initial installations of offshore structures.

Scene #11:

Impressed Current Cathodic Protection systems are typically used for applications with large current requirements.
These applications could be buried pipelines, large ships, retrofitting of offshore structures and concrete-rebar structures.
Impressed Current Cathodic Protection systems are also more cost-effective for structures buried in soil.

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About Allied Corrosion

Allied Corrosion Industries, Inc. is a full service corrosion control corporation providing design, installation and maintenance of corrosion solutions and cathodic protection systems since 1980. We are also a materials and test equipment provider, offering a full line of corrosion-related products.

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