Control of cathodic protection in bridges without disconnecting protection current: Passivity verification technique (PVT)

Abstract

Standards for monitoring the performance of cathodic protection systems on reinforced concrete structures actually recognised are based on the measurement of the polarised potential of the reinforcement (polarisation/depolarisation, E–log I tests). A new methodology to measure this performance has been developed based on the passivation of the rebar rather than on the level of potential polarisation. This new technique is based on electrochemical impedance spectroscopy measurements using a modulated confinement of the applied current. The results are not quantitative, but properly inform on the passivity of the rebar under protection and its resistance to corrosion. The new technique has been evaluated in the laboratory using sacrificial and impressed current systems. In the present paper results obtained with this technique were compared to results achieved by standard polarisation methods and were found to be in agreement. The new technique is faster than standard methods and does not require interruption of the cathodic protection current.