Which sequence correctly describes the dye penetrant inspection steps?

• A. Clean part, apply penetrant, soak for recommended dwell time, remove penetrant, and apply developer.
• B. Clean part, apply penetrant, soak for recommended dwell time, apply developer, remove penetrant.
• C. Clean part, apply penetrant, remove penetrant, soak for recommended dwell time, apply developer.
• D. Clean part, apply penetrant, soak for recommended dwell time, rinse, then apply developer.

Answer: (A)

Dye penetrant inspection works by using capillary action to pull penetrant into surface flaws and then revealing those flaws with a developer that creates visible indications. After the part is cleaned, you apply penetrant and let it dwell so it can seep into any cracks. It’s essential to remove the penetrant before applying the developer; the developer provides contrast by drawing out any penetrant still trapped in flaws, producing clear indications on the surface. If you apply developer while penetrant remains, or you rinse after dwell, the residual penetrant can smear or be washed away, making defects harder to see. Therefore the proper sequence is clean, apply penetrant, dwell, remove penetrant, then apply developer, and finally inspect under the appropriate lighting.