Wireless Corrosion Monitoring Sensors Based on Electromagnetic Interference Shielding of RFID Transponders

Electromagnetic interference (EMI) shielding is a common technology used to protect electronic devices from the interference of environmental noise or to prevent the radiation of electromagnetic waves from electronic devices to the environment. In this research, the EMI shielding principle was utilized to develop a simple and cost-effective wireless corrosion-monitoring sensor. A thin metal sheet (e.g., a steel foil) similar to the material to be monitored was attached onto the surface of a radio frequency identification (RFID) transponder and served as an RF shielding layer to block the communication between the RFID transponder and the transceiver. The shielded transponder (the sensor) was then subjected to corrosion exposure, which caused the corrosion of the shielding metal sheet and led to the degradation of the shielding effectiveness. By chronically recording the change of the RF signal strength and the amount of corrosion that occurred, a correlation could be established between the signal strength and the corrosion rate. In this way, a simple wireless corrosion-monitoring sensor was developed. Steel sheets with various thicknesses (50 μm to 250 μm) were used as shielding layers on ultra-high-frequency RFID transponders, and the sensors covered by these various sheets behaved differently during corrosion exposure. The microstructure change of the shielding material was characterized by optical microscopy and scanning electron microscopy, which revealed the uneven thinning and final damage of the shielding layer, leading to the (partial) restoration of the RF signal.