Holiday Testing is used when you need to know the exact condition of a coated surface. It works by attaching an earth lead to the substrate and then setting the unit to the required voltage setting as per the specifications. Once the unit is charged, the positive charged brush is swept over the entire coated surface. Any pores or under (DFT) thickness areas will cause an arc to occur exposing such defects in the coating.
This method uses current from 20KV, 40KV and 60KV for detection of porosity or under thickness coatings. It is able to be used on such things as, carbon impregnated coatings wrapping, carbonated rubber, thick coating such as rubber linings and over plastic / fibreglass type coatings likely to be come electrostatically charged. This system can also be used to determine if the required Dry Film Thickness (DFT) has been applied over the total covered areas.