Nondestructive Measurement of Coated Film-Steel Bond Strength Using Ultrasonic Resonance Frequency Method

Abstract

In order to nondestructively measure the bond strength of coated film on steel surface, ultrasonic resonance method using Fokker bondtester was investigated. The bondtester measures the change in the resonance frequency and the amplitude of the tester and coated film /steel system.
It was found that the resonance frequency difference between disbonded and bonded coating films on steel showed good correlation with the bondstrength of the bonded coating film on steel measured by a destructive method.
To applying this method widely, however, the following problems are to be solved in other ways.
(1) Differences arising from quite strongly bonded films on steel are too small to be detected.
(2) Film thickness variation causes changes in resonance frequency.
(3) Bond strength of films which deeply absorb ultrasonic sound is hard to be detected.
(4) Water uptake in film/steel interface causes resonance frequency change.