What Does Impressed Current Cathodic Protection (ICCP) Mean?
Impressed current cathodic protection (ICCP) is a corrosion protection system consisting of sacrificial anodes connected to an external power source. The external power source, often a DC power supply, provides the current necessary to drive the electrochemical reaction required for cathodic protection to occur.
In the absence of a DC power source, a transformer-rectifier connected to AC power can be used. Alternative sources may also be used to power the electrochemical cell, including wind, solar or gas-powered thermoelectric generators.
Impressed current cathodic protection systems are typically used in relatively large structures, where passive cathodic protection methods are ineffective or impractical. For example, passive cathodic protection is suitable for protecting individual structural members and appurtenances. However, this method generates minimal current, making it ineffective for protecting larger structures such as oil and gas pipelines and storage tanks.
Rather than depend on the natural potential difference between the anode and cathode material, ICCP systems use external sources to provide the necessary current. This increased current makes it possible for the cathodic protection to span a wider effective area.
While ICCP systems are more effective than their passive counterparts, they require more equipment and are also costlier to maintain.
Corrosionpedia Explains Impressed Current Cathodic Protection (ICCP)
The main difference between impressed current cathodic protection (ICCP) and passive cathodic protection (CP) is the presence of an external power supply. Both corrosion protection systems, however, operate on the same basic concept of bimetallic/galvanic corrosion.
Figure 1. Typical impressed current system.
How Impressed Current Cathodic Protection (ICCP) Works
To understand how ICCP works, it is essential first to understand the basics of bimetallic corrosion. Bimetallic corrosion, as its name suggests, is a type of corrosion that occurs when two different metals are paired together. During this unique phenomenon, one metal experiences accelerated corrosion while the other remains protected. To put it another way, one metal sacrifices itself so the other can last longer.
This is possible because the two metals form an electrochemical cell where one becomes the anode (the sacrificed metal) while the other becomes the cathode. By understanding this process, it is possible to force this type of reaction in real-life structures. By carefully selecting and pairing two different metals, we can purposely make an object the cathode, ensuring that it remains protected so long as it is connected to a sacrificial metal (the anode).
Benefits of Using ICCP
Some of the benefits of using ICCP include:
Larger effective protected area
ICCP is not dependent on the anode's electrode potential, which usually is not enough to cathodically cover large structures. Using an external power supply forces the electrochemical cell to work, allowing it to have a greater effective protection area.
Longer-term corrosion protection
Because electrode potentials do not play a significant role in ICCP systems, anodes can be selected based on other critical factors, such as current density, consumption rates, material cost and longevity. This allows asset owners to procure anodes that last longer, which can have an overall positive effect on repair and maintenance budgets.
Easier control and monitoring
The presence of an external power supply makes it possible to monitor and control the performance of the ICCP system. Operators can take monthly readings, allowing them to make the necessary adjustments to get the most out of the system.
While ICCP offers significant benefits over their passive counterparts, they can be more expensive because they require additional equipment during set up. Therefore, asset owners should assess the size and type of structure to be protected to decide if ICCP is the right corrosion protection solution.