Premature corrosion of a substrate is usually due to a coating failure. A common cause is the presence of flaws in the finished coating. Collectively referred to as porosity, the main types of flaws are: Runs & Sags, Cissing, Cratering, Pinholes, Over Coating and Under Coating.
When a coating is applied to a surface, a number of problems can occur which can cause problems later on in the life of the coating.
There are essentially three flaw detection methods; UV Pinhole Detection, Wet Sponge and High Voltage.
For effective testing, the output voltage must lie between certain upper and lower limits.
If the displayed voltage drops or the alarm sounds continuously, then the coating may be conductive.
Pulsed DC can be used to test for holidays over slightly conductive coatings, dirty or damp surfaces.
There are a wide range of probes available to suit all applications and substrates being measured.