The first step in conducting a liquid penetrant test on a painted surface is to

The first step in conducting a liquid penetrant test on a painted surface is to

• A. Dry and polish
• B. Apply penetrant
• C. Sand the surface
• D. Completely remove the paint

Answer: (D)

In liquid penetrant inspection, access to the surface beneath the coating is essential for the penetrant to enter any defects. Paint forms a barrier that blocks the penetrant from wetting cracks or porosity, so removing the paint exposes the substrate and allows accurate indication of flaws. Once the surface is bare, you can clean it, apply penetrant, wait, remove excess, apply developer, and inspect under proper lighting. Leaving the paint on would prevent defect indicators from forming or revealing them clearly, while sanding or simply drying and polishing wouldn’t make the penetrant reach any flaws. Applying penetrant over paint won’t give reliable results because the paint masks or blocks indications.

In liquid penetrant inspection, access to the surface beneath the coating is essential for the penetrant to enter any defects. Paint forms a barrier that blocks the penetrant from wetting cracks or porosity, so removing the paint exposes the substrate and allows accurate indication of flaws. Once the surface is bare, you can clean it, apply penetrant, wait, remove excess, apply developer, and inspect under proper lighting. Leaving the paint on would prevent defect indicators from forming or revealing them clearly, while sanding or simply drying and polishing wouldn’t make the penetrant reach any flaws. Applying penetrant over paint won’t give reliable results because the paint masks or blocks indications.