High and low voltage spark testing on painted; glass lined or coated pipes and vessels to detect damages of interior coating applications on surfaces. A test voltage is applied to the coating by moving a brush probe across the surface and where there is either a pinhole or flaw, the voltage will spark through the coating at the flawed location, a red flashing indicator will flash and an audible alarm will sound. The detected flaw can now be marked for subsequent repair and testing resumed for the remaining surface area. If no flaws are detected the test will therefore be non-destructive.
The value of the test voltage is determined by the dielectric or voltage strength of the coating thickness. As a rough guide the test voltage can be approximated between 3 to 5 volts per micron of coating thickness, therefore 1000 micron would be approx 3kV to 5kV test voltage.