Which non-destructive method uses infrared imaging to detect coating defects by temperature differences?

• A. Infrared thermography
• B. Ultrasonic testing
• C. Magnetic particle inspection
• D. Visual inspection

Answer: (A)

Infrared thermography detects coating defects by mapping surface temperature differences with an infrared camera. The camera measures the infrared radiation emitted by the surface and turns it into a temperature map. When a coating has defects such as delamination, voids, or moisture under it, heat flows differently through those areas, creating localized hot or cold spots on the surface. In active thermography, a heat source is applied and the way heat diffuses reveals underlying flaws as these temperature contrasts show up in the thermal image. This contrasts with methods that don’t rely on temperature changes. Ultrasonic testing uses sound waves, magnetic particle inspection relies on magnetic fields and iron particles, and visual inspection only assesses what’s visible on the surface—not subsurface conditions indicated by heat differences.