Corrosion Monitoring of Metal Alloys Using a Line-focus Ultrasonic Transducer System

Ultrasonic testing is a non-destructive testing method which is a promising approach for corrosion monitoring. In this research, a line-focus polyvinylidene difluoride (PVDF) ultrasonic transducer was fabricated and used to measure the Rayleigh surface wave velocity changes in commercial metal alloys during laboratory corrosion studies in simulated seawater. For isotropic solid materials, the elastic properties can be characterized from the measurement of the Rayleigh surface wave velocity. The experimental data acquired by the line-focus ultrasonic transducer system were analyzed, from which we found that the Rayleigh surface wave velocities and the Young's modulus decreased for 304 stainless steel, low-carbon steel and multipurpose 110 copper samples, while increased for 6061 aluminum alloy samples as the corrosion time increased during the experimental period. Clearly, the changing patterns of the Rayleigh surface wave velocity of the metal alloys during corrosion could provide part of the predictive solutions for assessment and mitigation of corrosion and the line-focus transducer system is promising for real-time monitoring of corrosion process.