This method can be used to find defects in insulating coatings complying with numerous norms including ASTM D4787 and ASTM D5162. It’s often employed for inspecting pipelines, tanks and other large structures.
For testing, one sets a certain test voltage on the POROSCOPE. The object to be inspected is connected to the ground (earth) cable, and the electrode is moved slowly over the object’s surface. If the electrode touches an opening in the coating, there’s a sparkover, which causes a capacitor to discharge in the device. The voltage drop is registered and an alarm indicates that the coating contains a pore.