Cathodic Protection of Arlington Memorial Bridge with Two-Stage Anodes

Arlington Memorial Bridge is a reinforced concrete spandrel arch bridge that connects Washington, DC and Virginia across the Potomac River. After over 85 years in service, the bridge started exhibiting signs of deterioration, including reinforcement corrosion. As part of a major rehabilitation effort to extend the bridge’s service life, targeted cathodic protection (CP) systems were installed in the arch cross-walls, floors, and under arches to mitigate and prevent corrosion. The implemented CP system consisted of galvanic and two-stage anodes to mitigate corrosion. Galvanic anodes were installed in the repair areas to prevent the ring anode affect and ensure a durable concrete repair. The two-stage anodes were installed in areas of concrete which were actively corroding without signs of concrete deterioration. The two-stage anodes initially deliver a charge to the reinforcement similar to an ICCP system to polarize the steel (Stage 1), after which they provide a maintenance amount of galvanic current sufficient to prevent corrosion (Stage2). Continuous monitoring of the two-stage anode performances showed their effectiveness in polarizing the steel and preventing corrosion activity. The Arlington Memorial Bridge rehabilitation shows that cathodic protection can be efficiently installed in a structure to provide a very effective and durable rehabilitation.

Learning Objectives:

1. Understand the two-stage anode technology.
2. Learn the design considerations for two-stage anodes.
3. Learn anode installation considerations for two-stage anodes.
4. Understand how two-stage anodes can be used to provide cathodic protection in an actively corroding reinforced concrete structure and their effectiveness in polarizing the steel.