Self-powered wireless corrosion monitoring sensors & networks

For an airtight civil engineering structure(for example, concrete beam), while a wire collection system is used for monitoring corrosion, the wire put inside concrete beam needs to prolong outside concrete beam to send the corrosion sensor’s information, which will accelerate the corrosion process because the wire’s laying possibly makes reinforcing steel inside the beam contact with air. Wireless sensor networks with wide application especially in structural health monitoring[57-60], matured in recent years represent an innovative solution to current corrosion monitoring systems, due to their low-cost, small size, low – power and wireless communication capability.

The most interesting and fascinating fact is that the corrosion process is an energy release process. This vital energy provides the possibilities to realize in-situ, real-time and on-line corrosion monitoring of RC structures by wireless energy-harvesting sensors and networks. We investigate deeply the generation of corrosion energy in RC structure and its availability as a power source. Powered by the energy harvested from corrosion environment, a new smart sensor platform is then designed to detect the corrosion status and report the samples via wireless links to the end user. Developing energy harvesting sensors is of critical importance for in-situ, real-time and on-line corrosion monitoring of RC structures because of its intrinsic capability of providing unbounded lifetime. This represents a tremendous step towards realization of practical corrosion monitoring.

Fora wireless sensor network, energy is usually provided from either solar power[61], structure vibration[62], chemical batteries, or lithium batteries. The wireless corrosion monitoring sensors need to be put inside concrete beam in an airtight way, which require that wireless sensor can work for a long time without outside energy supply as corrosion is a slow process(about tens years). Thus it is necessary to solve the problem of energy supply for the sake of monitoring corrosion with wireless sensor networks.

In the proposed self-powered wireless corrosion monitoring sensor network system shown in Fig.22[63], we use the electrochemical noise produced by corrosion not only as sensing signal but also as energy source for wireless sensor, the process of monitoring corrosion is the following: unit of gathering energy collect electrochemical noise, while energy reach the working requirement of wireless sensor, the other units of wireless corrosion sensor are in activation. Then micro-processing unit gathers and process the sensor signal-­electrochemical noise, the sensor signal processed is little in volume for wireless transmission because the energy needed by wireless transceiver unit is much more largely than the one of micro-processing unit. All the above units are put together inside airtight concrete structure to integrate into a self-powered wireless corrosion monitoring sensor, lots of such sensors forming self-organizing networks send their signal information to wireless base station. Wireless base station may receive the information and control the sensors,

Self-powered wireless corrosion monitoring sensors & networks
Self-powered wireless corrosion monitoring sensors & networks
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Self-powered wireless corrosion monitoring sensors & networksremote users can visited wireless base station to know the sensors’ status and corrosion information of monitored objective. The designed self-powered wireless corrosion sensor is exhibited in Fig.23[64].

electrochemical

micro-processing

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transceiver unit

Подпись: Fig. 23. Self-powered wireless corrosion monitoring sensor

Fig. 22. Self-powered wireless corrosion monitoring networks

5. Application of the corrosion monitoring system in civil engineering

5.1 Corrosion monitoring of the RC beams

The corrosion sensors presented in the previous sections have been applied to monitor the corrosion status of the RC beams (see Fig.24). The electrochemical measuring techniques which are seemed as the software for corrosion monitoring based on galvonastatic step excitation and electrochemical noise have been developed to extract the characteristics of general corrosion and pitting corrosion, respectively[65].