Pinhole
Pinhole turns up in 2 fields: powder coating, nonwovens. Here is what it means to the people in each one.
Pinhole in powder coating
A tiny hole running through the cured film, often down to bare metal.
Pinholes come from gas escaping during cure, from outgassing substrates, moisture in the powder or on the part, HAA systems at high build, or air trapped in heavy films. They let corrosion reach the metal and are unacceptable on outdoor or immersion work. Many show only under magnification or with a holiday detector, and they cluster on castings, welds and edges.
"Got pinholes all along the weld seams, either moisture in the seams or the weld's porous."
Pinhole in nonwovens
Tiny hole in a barrier fabric or film that lets liquid or particles through.
Pinholes in SMS and meltblown come from shot, thin spots, drips burning through or contamination, while pinholes in film come from gels and overstretching. Even a few per square meter can fail a barrier spec. They are found with light tables, inline cameras and hydrohead testing.
"Pinholes are showing on the light table every couple of meters, so the MB layer is running too thin."