Real-time Non-Destructive Erosion Monitoring of Coatings using Passive Microwave Split Ring Resonator Sensor

Coating erosion/corrosion detection and its real-time monitoring can provide an early alert of physical damages to the coated structure. This work presents a real-time, contactless, and low-cost coating health monitoring system using passive microwave Split Ring Resonator (SRR) sensor. The sensor operates at a resonant frequency of 2.5 GHz, with a resonant amplitude of −23 dB and a 3 dB Quality factor of 120. The sensor's performance is examined by analyzing its response to physical erosion of a 2.4 mm thick epoxy resin coated over the SRR. The sensor demonstrates a resonant frequency upshift at an average rate of 3 MHz / 30 um of erosion depth. The increase in the resonant frequency is due to the reduction of the effective permittivity in the sensor's vicinity caused by the decrease in coating thickness. The presented real-time and microwave-based coating erosion monitoring sensor system could find consumer applications in automobiles, painted structures, and pipelines. In addition, the developed sensor can be easily integrated with embedded systems making them a potential low-cost sensor for home Internet of Things (IoT).