Embedded Galvanic Anodes for Targeted Protection in Reinforced Concrete Structures, Ball & Whitmore

Corrosion of reinforcing steel in concrete is a major cause of structure maintenance and repair. Oxidation at the anodic sites on the steel reinforcement causes expansive forces that leads to visible concrete distress such as rust stains, cracks, spalling, or delaminations. Corrosion can also cause delaminations in the concrete cover (which may not be visually apparent), potentially with large sections of concrete dislodging from the structure.  Additionally, loss of section due to reinforcement corrosion can cause structural issues.  Advancements in concrete repair methods and corrosion mitigation systems have given structural engineers many options to repair and extend the service life of actively corroding structures. Today, most structures suffering from corrosion can benefit from some level of electrochemical corrosion protection.
In some cases, a global protection strategy using electrochemical chloride extraction, impressed current cathodic protection, or galvanic protection is a preferred solution. Global protection should be considered if: 1) a long service life is desired; 2) corrosion activity is widespread; 3) the structure is considered to be critical in nature; 4) access is difficult and/or cost of future repairs are high; or 5) a high level of protection is required over large areas.  n other cases, corrosion is not widespread or budget limitations prevent a more comprehensive approach from being implemented. In these cases, implementing a targeted corrosion mitigation approach is generally preferred rather than not providing any protection whatsoever. Targeted corrosion protection can be economically implemented to provide an extension of service life at a moderate incremental cost and reduce the risk of serious corrosion damage.
For almost a decade, embedded galvanic anodes in a discrete or “point” form have been used to provide localized corrosion prevention around concrete repairs. Embedded discrete anodes are installed around the perimeter of the concrete repair as close as practical to the patch edge. The anode units are prewet and tied directly to the reinforcing steel. The anode spacing is dependent on the amount of steel protected, but is generally in the range of 12 to 24 in. (305 to 610 mm).
For over 5 years, galvanic anodes in a ribbon or strip form have been used to provide protection in reinforced concrete. As opposed to discrete or point anodes, these anodes are referred to as distributed anodes and are provided in various shapes and lengths up to 7.5 ft (2.3 m).  Distributed anodes are placed across the surface of the concrete to be protected then embedded in a reinforced concrete jacket or overlay. The distributed anode systems are used to provide galvanic protection over a larger area but can be easily used to protect small structural elements such as a single pile, column, or wall. This type of system can also be referred to as a galvanic encasement.  (read more)