Impressed Current Cathodic Protection

Cathodic protection is a technique used to control the rate of corrosion of a metal surface, usually a piece of equipment used in the home or a larger piece of industrial equipment. The system works by turning the surface of the metal itself into the cathode of an electrochemical cell. In simple terms, this means connecting the piece of metal which is to be preserved to a lesser, unprotected, piece of metal which is to be “sacrificed” to corrosion.

 

Where Is Cathodic Protection Most Commonly Used?

As noted above, systems of cathodic protection are used in all manner of industrial and home use applications. For example, the steel pipes in most home plumbing systems, as well as hot water heaters, are commonly treated with cathodic protection in order to safeguard them from rusting out. Other uses are primarily in industrial environments, such as the hulls and piping of gas and oil pipelines, seagoing vessels, offshore oil rigs, and the like.

 

eng-cathodic-protection-systemImpressed Current Cathodic Protection

When dealing with much larger structures, particularly those where the level of electrolyte resistivity will be much higher than normal, a special system of impressed current cathodic protection will need to be employed. This will be necessary because the normal system of galvanic anodes will simply not be able to deliver the necessary amount of current in order to provide protection. Of course, if stressed hard enough, results can be delivered through a normal system of galvanic anodes, but the results will be inefficient, both from the standpoint of energy usage and economic outlay.

 

Creating And Using A Cathodic Protection System

An impressed current cathodic protection system (see Cathodic Marine) consists of a series of anodes which are then connected to a source of DC power. Usually, this will be in the form of a transformer-rectifier that has been independently connected to a source of AC power. If an AC power source is not available, there are other sources which can be fitted up to the purpose. For example, solar powers have been used in the past to provide the necessary source of power. Other possible sources of energy are wind power, as produced from small turbines. Occasionally, good results have been produced with the use of even gas powered thermoelectric generators.

 

How Long Will Cathodic Protection Last?

The results of treating pipes and other metal surfaces with cathodic protection have been uniformly positive. Depending on the age and level of exposure of the pipe or other metal surface in question, the results of cathodic protection treatment can last anywhere from several years to a decade. Frequent inspections will still be necessary to ensure that the treatment is taking its full effect.