Dye Penetrants improve the sensitivity of visual inspection by increasing the contrast of surface breaking discontinuities with the background colour of the test surface. Penetrants are liquids of intense colour which are drawn into surface-breaking cracks and cavities by capillary action. After a suitable contact time excess penetrant on the surface is carefully removed. Penetrant left within cracks and cavities bleeds onto the surface. A fine coating of white developer powder is applied to the surface to increase bleed-out and improve contrast.


Rod Rigging
Fatigue cracks on cold-heads.

Other materials
Fatigue, stress & corrosion cracks.
Weld cracks of heat affect zone.
Poor weld penetration.


Liquid Dye Penetrant can only be used on surface-breaking defects in non-porous materials.

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