PERFORMANCE OF A CONDUCTIVE-PAINT ANODE IN CATHODIC PROTECTION SYSTEMS FOR INLAND CONCRETE BRIDGE PIERS IN VIRGINIA

As part of efforts to identify effective and durable anodes for use in cathodic protection of different reinforced concrete members, a water-based conductive paint was tested in two cathodic protection (CP) systems that were built, one 8 years ago and the other 6 years ago, to protect the concrete piers of twin inland bridges in Virginia. Measurements made at various times of circuit current, voltage, rebar potential, and 4-hour polarization indicated that the CP systems were providing more than sufficient protection to the rebars. Natural paint deterioration (peeling, cracks, stains, etc.) that was observed in the conductive paint ranged from 0% to 0.37% in the older system and 0% to 0.14% in the newer system. Most of the deterioration was located at the exposed ends of the pier caps. Overall, the performance of the conductive paint indicated that (1) earlier prediction by some experts of premature failure of the paint once it is polarized is unwarranted, and (2) barring any extremely rapid paint deterioration in the future, it is a reasonable estimate that the service life of the conductive paint is at least 15 years--especially if minor paint deterioration is touched up as early as possible.