Liquid penetrant testing applies a thin dye to a cleaned surface, lets it soak into open flaws for a dwell time, often 10 minutes or more, removes the excess and applies a white developer that pulls the dye back out as visible indications. It works on any nonporous material, including stainless, aluminum and titanium, but finds only discontinuities open to the surface, and the surface must be thoroughly cleaned first.
Do PT on the stainless root after grinding, red dye, ten-minute dwell, then developer.
Grinding or blasting smears metal over crack openings, so stainless often needs an etch before PT will find anything.
Also heard as
- dye pen
- dye penetrant
- liquid penetrant
- LPT
Related terms
MT
Magnetic particle testing: finding surface and near-surface cracks in steel with a magnetic field and iron powder.
VT
Visual testing: inspecting welds by eye with gauges, lights and magnifiers, the first and most-used NDE method.
Arc strike
A spot where the arc touched base metal outside the weld, leaving a small melted or hardened scar.
Hydrogen cracking
Delayed cracking in steel welds caused by hydrogen, hard microstructure and stress acting together.