Embeddable corrosion rate-measuring sensor for assessing the corrosion risk of steel in concrete structures

New and rehabilitated concrete structures \need assessment of corrosion rate (CR) of rebars more precisely to ensure efficiency of protection against corrosion. For assessing the corrosion status, different sensors have been developed to reduce the risk of undetected corrosion problems. An embeddable CR-measuring sensor is embedded either closer to the rod during the construction of a new structure or in drilled holes in old structures so as to generate reliable data. In the present paper, the accuracy in predicting the corrosion current (I-corr) by embeddable sensor was assessed by comparing with other conventional electrode arrangements. I-corr was assessed under passive and active conditions of rebar. The presence of a cross bar and the effect of cover on I-corr were also studied. Using linear polarization resistance (LPR) technique and electrochemical impedance spectroscopic (EIS) technique, the CR was determined and compared with the weight-loss method. Results concluded that by using electrochemical impedance technique, developed embeddable sensor is able to predict the CR very close to the CR determined from gravimetric method. The deviation from an ideal linear curve and the higher interfacial capacitance of steel in concrete caused the LPR method to underestimate the CR of rebar. The presence of the cross bar increases the I-corr of the main bar by 4 times in a passive state of the rebar and it has no effect if the rebar is in an active state. The embedded sensor, though having smaller counter electrode (CE), polarizes the rebar up to 2 times the length of CE under both active and passive states. Copyright (c) 2008 John Wiley & Sons, Ltd.