Non-Destructive Subsurface Inspection of Marine and Protective Coatings Using Near- and Mid-Infrared Optical Coherence Tomography

• Main Authors: Christian R. Petersen, Narayanan Rajagopalan, Christos Markos, Niels M. Israelsen, Peter J. Rodrigo, Getinet Woyessa, Peter Tidemand-Lichtenberg, Christian Pedersen, Claus E. Weinell, Søren Kiil, Ole Bang
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Coatings
• Subjects: non-destructive testing; non-invasive; OCT; 3D imaging; subsurface inspection; underfilm
• Online Access: https://www.mdpi.com/2079-6412/11/8/877

Near- and mid-infrared optical coherence tomography (OCT) is evaluated as a non-destructive and non-contact reflection imaging modality for inspection of industrial and marine coatings. Near-infrared OCT was used to obtain high-resolution images (~6/2 µm lateral/axial) of hidden subsurface cracks and defects in a resin base coating, which had been exposed to high pressure and high temperature to study coating degradation in hostile environments. Mid-infrared OCT was employed for high-resolution (~15/8.5 µm lateral/axial) subsurface inspection of highly scattering marine coatings, demonstrating monitoring of wet film thickness and particle dispersion during curing of a 210 µm layer of antifouling coating, and detection of substrate corrosion through 369 µm of high-gloss alkyd enamel. Combining high-resolution and fast, non-invasive scanning, OCT is therefore considered a promising tool for studying coating performance and for industrial inspection.