Passive Surface Acoustic Wave Sensors for Early Corrosion Onset Detection

Abstract

Corrosion creates serious safety concerns and economic burden in fuel processing and transportation. Being able to monitor the infrastructures in real time and detect corrosion onset may prevent potential consequences resulting from their failure. Passive wireless surface acoustic wave (SAW) devices are promising passive devices to detect the presence of water and corrosion onset amongst other parameters in natural gas pipelines and wellbore tubes. Here, we present on the possibility of using shear horizontal (SH-) SAW devices for monitoring metal film dissolution in hydrochloric acid of varied pH. 520 MHz SH-SAW reflective delay lines with two reflectors were fabricated on 36°Y-X LiTaO3, of which a channel was coated with 60 nm thick iron film by magnetron sputtering. With the film, the sensor had a center frequency of 529.8 MHz when measured in air. The sensor showed a slight attenuation and small frequency shift in DI water. In HCl solution with pH 2.01, the sensor’s center frequency first decreased with time for the first six minutes to reach down to 521 MHz and then remained almost unchanged. The S11 magnitude also showed similar behavior. After ten minutes immersion into the corrosive solution, no iron film was left under a visual inspection. The decrease in the frequency and attenuation is probably due to the changes in the mass and elasticity and the film surface roughening, respectively. Observed initial results are promising towards the implementation of SAW devices for monitoring corrosion in metallic structures in real time.