How are non-metallic coatings evaluated for integrity in hot-section components?

• A. Tasting the coating.
• B. Visual inspection, borescope, thickness measurements, and NDT to detect delamination or cracking.
• C. Measuring weight.
• D. Ignition test.

Answer: (B)

Non-destructive evaluation of hot-section coatings centers on detecting where the coating has separated, cracked, or thinned, without damaging the part. Visual inspection catches obvious surface damage such as cracks, chips, or spall near edges. A borescope lets you look into tight passages and internal surfaces where coating problems may hide. Measuring coating thickness ensures the layer remains within design limits—too thin can fail to protect, too thick can cause stresses or spalling. NDT methods are used to find subsurface flaws like delamination or cracks that aren’t visible on the surface, providing information about adhesion and integrity without harming the component.

Tasting is unsafe and not diagnostic, measuring weight doesn’t reveal internal coating health, and an ignition test would destroy the coating and isn’t a valid integrity check.