Which non-destructive test uses a colored spray to reveal imperfections in a weld?

• A. Dye-penetrant test
• B. Radiographic test
• C. Ultrasonic test
• D. Magnetic particle test

Answer: (A)

Colored spray reveals imperfections by applying a penetrant liquid that is drawn into surface-breaking flaws, such as cracks or porosity, in the weld. After allowing time for penetration, the surface is cleaned and a developer is applied; the penetrant that remains in the flaw bleeds out and becomes visible as a colored indication, making tiny defects easy to see under normal lighting (or under UV light if fluorescent penetrants are used). This method is specifically suited for detecting surface-breaking flaws in welds without damaging the part. Other non-destructive tests use different principles: radiographic testing images internal features with X-rays; ultrasonic testing uses sound waves to detect flaws inside the material; magnetic particle testing uses magnetic fields and iron particles to reveal surface and near-surface defects in ferromagnetic materials.