Testing for Pinholes with the Wet Sponge Method using the Elcometer 270 Pinhole Detector
When testing for pinholes on thin coatings, powder coatings, and other applications where you do not wish to damage the coating; typically the wet sponge technique, also known as the low voltage pinhole method, is used.
The wet sponge technique is a quick and simple method for testing insulation coatings less than 500 microns (20 mils) thick on conductive substrates. Put simply, a low voltage no bigger than 90 volts is applied to a damp sponge.
When you pass the sponge steadily over the coating, liquid from the sponge is drawn through any pinholes by capillary action; and when it touches the bare substrate, the current flows from the detector, through the substrate, and back to the detector through a signal return lead, which is clipped to an uncoated section of the substrate. This completes a low voltage circuit, setting off an alarm on the detector, letting you know where you have a pinhole.
Pinholes are important to detect because they are a small hole which goes all the way to the substrate that acts like a capillary tube, drawing moisture drops down to the steel through capillary action – where liquid can flow through narrow spaces without gravity - accelerating the process of corrosion.
The Elcometer 270 Pinhole Detector provides both visual and audible alarms when a flaw is found, and it is incredibly easy to use.
To maximise the efficiency of the Elcometer 270 Pinhole Detector, you can add a surfactant to the water. Using a surfactant will significantly reduce the surface tension of the water, allowing the moisture to penetrate the smallest of pinholes.
The Elcometer 270 Wet Sponge Pinhole Detector is available in either dual or triple voltage models. The dual voltage model can be set to 9V, for testing thin coatings up to 300 microns (12 mils) thick; and 90V, for coatings up to 500 microns (20mils). The triple voltage model can also test at 67.5V, the US standard test requirement.
The Elcometer 270 Pinhole Detector is available as part of a Pinhole Detector Inspector’s Kit; which includes the various wand adaptors, spare sponges, surfactant, and a 10m signal return cable. Simply choose your preferred model of Elcometer 270 Wet Sponge Pinhole Detector, and you have everything you need for low voltage flaw detection.
Testing on coatings up to 500 microns (20 mils) thick, the Elcometer 270 Wet Sponge Pinhole Detector is the ideal gauge for detecting pinholes.