Field Experience with Rebar Probes to Monitor Performance of Sprayed Zinc Galvanic Anodes on Concrete

Sprayed zinc galvanic anodes have shown promise as low-cost alternatives to simple gunite repair or even impressed current systems for corrosion-damaged marine substructure of bridges. Because the anodes are permanently connected to the rebar assembly at many points, it is not normally possible to deenergize the anode for measurement of steel polarization and current delivery. Field performance of these systems has been monitored with short embedded rebar probes fitted with external switchable connections. This has allowed for current density, depolarization decay, and polarized potential measurements as a function of time. The anode current delivery has also been measured with isolated cutout anode regions “windows”, and in one case with a specially designed, fully disconnectable anode. The results of the different means of evaluating system performance over several years are compared for various field installations in Florida. The relative merits of the monitoring methods and the information they provide on the corrosion condition of the steel are analyzed.