Passive, wireless corrosion sensors for reinforced concrete structures

Corrosion of steel in reinforced concrete structures is a costly problem. Effective planning is required to raise the considerable capital expended annually on the repair and replacement of structures damaged by corrosion. Essential to this planning is knowledge that corrosion has initiated in a given structure. The passive, wireless corrosion sensor is a technology that could potentially provide this knowledge of initiation of corrosion, both economically and reliably. The sensor, which consists of two resistor-inductor-capacitor circuits, requires no onboard power supply or wires to send a signal. The signal of the sensor is obtained by magnetic coupling with a reader coil. As a threshold sensor, the sensor has a binary output with one signal indicating that corrosion has not initiated and another signal indicating that corrosion has initiated. Multiple designs of the sensor have been tested in concrete and reinforced concrete structures, some full-scale, subjected to extreme environmental conditions over long durations. Certain designs have proved highly reliably at indicating the initiation of corrosion, verifying the concept of the passive, wireless corrosion sensor.