Application of ACFM for inspection through metal coatings

摘要

ACFM is an electromagnetic NDT technique used to inspect metal structures for surface-breaking cracks, through a variety of non-conductive coatings. However, if the coating is conductive, such as flame-sprayed aluminium or zinc galvanising, the electromagnetic surface properties of the structure are altered. These metallic coatings were modelled using Comsol multiphysics, and the model verified by experiments with metal-coated samples. The results show that accuracy of sizing is decreased, depending on coating thickness and whether the crack penetrates through the conductive coating or not. If the metal coating thickness is too thick, then defects may be completely masked.