Analysis of reflected terahertz time domain waveforms for the detection of coating delamination

Corrosion presents significant economic implications across various industries. Its impact is far-reaching, affecting infrastructure, transportation, manufacturing, and energy sectors. To combat this problem, new coatings are being developed that must adhere well to the metal surface, have minimal thickness, and resist delamination over time. The adhesion of the coating is key to achieving its design lifespan, and coatings applied according to the manufacturer's recommendations typically offer good adhesion to the substrate and can resist corrosive agents. The adhesion of the coating is dependent on various factors, including coating properties, substrate cleanliness, surface roughness, and pre-treatments before application. Here, we present a recent study that explored the impact of surface roughness profile morphology and height on the pull-off adhesion strength value of the coating and its correlation with interfacial adhesion at the coating and substrate. The study revealed that delamination of coatings on steel can be detected using terahertz reflection spectroscopy, which correlates well with standard industry pull-off testing. The findings suggest that THz reflection spectroscopy can be used for non-destructive testing of anticorrosion coatings and the aging process.