J. H. Bae, T. H. Ha, Y. C. Ha, H. G. Lee, D. K. Kim, Korea Electrotechnology Research Institute, Changwon, South Korea; S. Muralidharan, Central Electrochemical Research Institute., Tamilnadu, India
Attempts have been made to fabricate embeddable type sensor electrodes for corrosion monitoring of reinforcements in concrete structures. Cylindrical titanium surface activated with mixed metal-metal oxides (MMO) [though similar to permanent impressed current titanium anodes used in cathodic protection] and alkaline manganese dioxide (MnO2) are fabricated in the laboratory as suitable as an embeddable use. The performance characteristics were evaluated in a saturated calcium hydroxide solution (pH 12.5), a synthetic concrete pore solution (pH 13.5) and ordinary Portland cement extracts (pH 13.0), which corresponds to the concrete environments. Sensors are embedded into the cement mortars and concrete and the electrochemical stability was monitored for the long term exposure periods of 2 years. Further the polarisation behaviour and impedance characteristics of the sensors embedded in mortar and concrete was carried out in three aqueous solutions namely distilled water, 3% NaCl and natural sea water. This investigation fulfill the results obtained from the MMO and MnO2 sensors in concrete environments, mortar and concrete subjected to natural weathering condition for the exposure period of 2 years.
MnO2 sensor seems to be the more stable and reliable potential sensor electrode in concrete medium and also in concrete structures. Unlike conventional reference sensors, MnO2 sensor is free from harmful elements like mercury and corrosion accelerators like sulphate and chloride. Advantageously MnO2 sensor was able to use an embeddable type into new and old structures.
Reference: Tae-Hyun Ha, Srinivasan Muralidharan, Jeong-Hyo Bae, Yoon-Cheol Ha, Hyun-Goo Lee, Kyung-Wha Park and Dae-Kyeong Kim, Role of Sensors in Corrosion Monitoring and Durability Assessment in Concrete Structures: the State of the Art, Sensors and Materials, Vol.16, No.3, (2004) 133–158.
Summary: Attempts have been made to fabricate embeddable type sensor electrodes for corrosion monitoring of reinforcements in concrete structures. Cylindrical titanium surface activated with mixed metal-metal oxides (MMO) [though similar to permanent impressed current titanium anodes used in cathodic protection] and alkaline manganese dioxide (MnO2) are fabricated in the laboratory as suitable as an embeddable use.
