Non-Destructive Testing and Imaging of Marine Coatings using High-Resolution Mid-Infrared Optical Coherence Tomography

Coatings science is constantly in development to meet the increasingly demanding requirements of the maritime industry. Consequently, there is a growing need for non-destructive testing (NDT) and imaging of coatings at all stages during development and deployment. One imaging technique which has the potential to offer both noncontact measurements and high spatial resolution is optical coherence tomography (OCT). OCT is a reflection modality method based on the interference of light reflected/scattered from different depths of a sample. Because it is based on low intensity laser light it can reach microscopic resolution, is non-destructive, and does not require a contact medium, which also enables measurements on wet coatings. There has been few reports of OCT being applied for inspection of paints and coatings, primarily for cultural heritage preservation, but also for automotive and pharmaceutical coatings [1] – [3] . Marine coatings in particular make use of functional additives, which are highly scattering to visible and near-infrared light, and so there is a need for developing OCT systems based on longer wavelength mid-infrared light to improve the penetration depth.