Cathodic Protection Solutions for Electric Utility Structures

During the course of their service-life direct embedded steel transmission and distribution structure foundations are subject to significant environmental exposure that can, over time, have a negative impact on their strength and structural integrity. Foundations are critical components and are therefore crucial to the long-term performance and reliability of a utilities overall transmission and distribution systems. Because of the aging infrastructure in the United States relative to the national power grid many of these existing structures are now beyond their original designed life span. As such, options for extending the service life of existing structures and even adding additional protection to newly installed structures is becoming more of a necessity. Corrosion control measures can be effective and economical solutions to help protect structures both above and below ground. In many instances coatings make up the primary means of corrosion protection measures. However, most coatings contain flaws or “Holidays” that allow exposure of the structure to its environment. When coatings alone are not sufficient to protect from the effects of corrosion cathodic protection is an additional measure of protection that can be applied. Cathodic protection (CP) is an advanced secondary means of corrosion control used for the protection of metal structures which are submerged or buried. CP systems are most commonly used to help protect large structures such as pipelines, storage tanks, ships, and offshore platforms. However, these systems can be readily adapted to perform well on smaller structures like steel transmission and distribution support structures. CP works by transferring the corrosion activity that would normally occur on the structure to sacrificial anodes with a higher electrochemical potential than the alloy being protected. This is achieved by placing the anode within the same electrolyte (soil, water, swamp, etc.) as the structure and placing it in electrical contact with the structure. Once applied most CP systems typically require little in the form of maintenance. However, monitoring system performance should be maintained to ensure protection.