Before UT testing a rolled or forged surface with a thin scale that adheres, which step is necessary before testing?

• A. Clean the surface of loose scale
• B. Have all scale removed
• C. Rough machine the surface
• D. Caustic etch the surface

Answer: (A)

Before UT, you must ensure a good acoustic interface between the transducer and the part. Loose scale on a rolled or forged surface can trap air and create gaps, which disrupt the ultrasonic beam, degrade signal quality, and can hide or imitate flaws. Cleaning away the loose scale removes these barriers so the coupling medium can contact the surface cleanly and the ultrasonic energy can propagate reliably. You don’t need to remove every bit of adhered scale if it’s firmly bonded, and roughing the surface or chemically etching it isn’t part of standard UT surface prep for this scenario. The key step is to clean off the loose scale to permit proper coupling and accurate testing.