Performance of zinc sacrificial anodes for long-term control of reinforcement corrosion

Abstract
Since its development in the mid-nineties, numerous installations of the alkali activated zinc sacrificial anodes have been carried out in repairs to steel reinforced concrete structural elements suffering from corrosion. From these, several sites have been thoroughly monitored in the UK and worldwide. Results so far have been very encouraging with current densities ranging between 0.8 mA/m² and 10 mA/m² of steel surface depending on the type of application which includes cathodic prevention, corrosion control and cathodic protection. These levels of currents were shown to be sufficient to overcome any further visible corrosion of the steel reinforcement extending the service life of the repairs significantly. Some of the early field projects have now been monitored for more than ten years. This presents an opportunity for the results to be analysed and the performance of the sacrificial anodes to be critically assessed medium to long term.
This paper reviews the performance of the anodes in terms of current output and steel polarization levels over the years in site trials, field projects and 14 year old laboratory concrete slabs. The prospects of a further recently developed improved sacrificial anode system achieving improved performance are reviewed and discussed.