Premature corrosion of a substrate is usually due to a coating failure. A major cause is the presence of flaws in the finished coating, collectively referred to as porosity. One of the most obvious porosity issues would be pinholes - where the substrate is open to the elements through the pinhole. Pinholes are caused by air entrapment, which is then released from the surface, or by the entrapment of particulates (dust, sand etc.) which do not stay in place. Pinhole detection is therefore essential to monitor the integrity of the protective coating from its initial application, throughout its service life. Pinhole Detectors are the ideal solution to detect flaws and pinholes on a coating.
Elcometer offers a range of Pinhole Detectors from the low cost UV Pinhole Detector Flashlight to the full Pinhole Detector Inspectors Kit.
Pinhole detection methods explained
A low voltage is applied to a moist sponge. When the sponge moves over a coating flaw, liquid penetrates to the substrate and completes an electrical circuit, setting off the alarm. The wet sponge technique is suitable for measuring insulating coatings less than 500µm (20mils) on conductive substrates, and is ideal for powder coatings and other coatings where the user does not wish to damage the coating.
The Elcometer 270 pinhole detection range utilises the wet sponge technique and sets the standard for wet sponge detectors - high quality, low voltage detectors with a wide range of accessories.
UV light can be used as a low cost, quick method of detecting pinholes in coatings. A base coat containing a UV fluorescing additive is applied. When the UV flashlight shines on the coating, areas where the base coat is not covered fluoresce, identifying the location of the pinhole.