Which non-destructive test is commonly used to detect coating delamination beneath turbine blade coatings?

• A. Magnetic particle inspection detects surface coating delamination.
• B. Visual inspection detects delamination under coatings.
• C. Ultrasonic thickness testing detects coating thickness and delamination under coatings.
• D. Radiographic testing detects delamination under coatings.

Answer: (C)