Pinhole
Detection
Metals,
especially steel, are liable to corrode unless they are covered by a protective
coating. Coatings such as paint, plastic and rubber protect metal against
corrosion provided that the coating is free from pinholes and
porosity.
Using
high voltages detects these defects. The PoroTest 7 uses a defined high voltage
to generate a spark to cross an air
gap, e.g. a pinhole in the coating thus indicating an area of the coating where
a defect is present.
Another approach is the
wet sponge method which is suitable for inspecting individual layers applied
over metallic substrates. The PoroTest 1 uses a 9V direct current, and is
completely risk free but is limited to coatings that are 12 mils
max.
