Long-term relative performance of embedded sensor and surface mounted electrode for corrosion monitoring of steel in concrete structures

Embedded half-cell potential sensor (MnO2) and corrosion rate monitoring probe sensor (LPR) were assembled and evaluated their performance in reinforced concrete structures under active and passive condition of steel reinforcements. The relative performance of the embedded and surface mounted systems was studied. The half-cell potential of embedded MnO2 sensor in concrete was found to be consistent and showed perfect stability for an exposure period of 24 months. Potentiodynamic polarization parameters such as Ecorr and Icorr for steel in active condition are more than that of passive condition and thereby embedded sensor clearly distinguished the chloride-contaminated concrete. Impedance studies also revealed that the solution resistance of concrete with embedded sensor is negligible but is very large for surface mounted system. The Icorr values obtained for steel in concrete for embedded corrosion rate monitoring probe sensor was 1.76 × 10−4 mA cm−2 whereas for surface mounted guard ring system was 5.10 × 10−4 mA cm−2. Embedded system showed 2.89 times the lesser corrosion rate than the surface mounted system. For service life prediction of field structures, precise measurements of corrosion rate of a steel reinforcement are a pre-requisite. In such cases embedded corrosion rate monitoring probe sensor accurately predicts the corrosion rate of steel reinforcements in concrete.