Monitoring the boundary of an adhesive coating to a steel substrate with an ultrasonic Rayleigh wave

Abstract

Abstract Coating–substrate adhesive joints are used in mechanical engineering and automotive vehicle construction. Monitoring their condition, both at the manufacturing and operational stages, is important for durability and extended lifetime. The article proposes a method for continuous monitoring of the state of the coating–substrate joint using ultrasonic surface wave. The waveforms of ultrasonic parameters such as gain of pulse of ultrasonic wave, resonant frequency and bandwidth over the lifetime of the tested joint were determined. The resonant frequency change precedes the final stage of degradation of the coating–substrate connection, which leads to complete detachment of the coating from the body sheet. Both, during the period of constitution and degradation, rapid changes in the pulse gain of the ultrasonic surface wave were recorded. The knowledge about the waveforms of the selected ultrasonic wave parameters makes it possible to assess the condition of the joint and is the basis for deciding on its further operation or repair.