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Corrosion induced metal loss is the primary cause for the failure and destruction of steel structures. Traditional methods such as corrosion coupon method and electrochemical methods are difficult to realize online monitoring of corrosion. In this paper, the piezoelectric impedance intelligent sensing method and monitoring technology for the corrosion monitoring of steel structures were proposed. The corrosion sensor was consisted of a piezoelectric patch laminated with a metal plate, and it operates based on the piezoelectric impedance coupling and corrosion-sensitive feature in its resonance. Firstly, based on the linear piezoelectric elasticity theory and the Kirchhoff thin plate assumption, a theoretical model of piezoelectric impedance for the piezoelectric-metal laminated structures was derived. Secondly, finite element simulation and experiments were carried out to validate the corrosion sensing mechanism and investigate its response under accelerated corrosion tests. Thirdly, to achieve high durability, the packaging structure of the sensor was designed with optimized sensor parameters. Lastly, a cloud based wireless impedance monitoring system was developed and its performance was examined in an outdoor corrosion monitoring of a steel structure. The results demonstrated that the resonant frequency of the sensor has good linear relationship with corrosion induced thickness loss.
