Why is it possible to flush a surface with a coarse water spray to which a water-washable penetrant was applied, remove the excessive penetrant, and not remove the penetrant that is in the defects?

Why is it possible to flush a surface with a coarse water spray to which a water-washable penetrant was applied, remove the excessive penetrant, and not remove the penetrant that is in the defects?

• A. The water droplets are relatively large and will not enter most defect openings
• B. The surface has no defects
• C. The penetrant in defects is chemically bonded to the surface
• D. The defect openings are sealed by the holder

Answer: (A)

When penetrant enters a defect, it is drawn into narrow openings by capillary action and becomes trapped inside the defect geometry. A coarse water spray uses relatively large droplets that wash across the surface but don’t readily enter or evacuate those tiny defect openings. So the rinse removes the excess penetrant on the surface, while the penetrant that is already in the defects stays in place because the capillary forces and geometry hold it there. The developer can later draw that penetrant out to reveal the flaw. The other options don’t fit because the retention inside defects isn’t due to chemical bonding with the surface, and the concept isn’t about the surface being defect-free or openings being sealed.

When penetrant enters a defect, it is drawn into narrow openings by capillary action and becomes trapped inside the defect geometry. A coarse water spray uses relatively large droplets that wash across the surface but don’t readily enter or evacuate those tiny defect openings. So the rinse removes the excess penetrant on the surface, while the penetrant that is already in the defects stays in place because the capillary forces and geometry hold it there. The developer can later draw that penetrant out to reveal the flaw. The other options don’t fit because the retention inside defects isn’t due to chemical bonding with the surface, and the concept isn’t about the surface being defect-free or openings being sealed.