How to Calculate the Voltage for a Spark/Holiday Test for Epoxy Paint Coatings

A high voltage 'spark test' Holiday Detector is used to detect any weak spots in coatings.

A high voltage 'spark test' Holiday Detector is used to detect any air bubbles, inclusions, thin spots, bridging, hairline cracks, etc. in coatings. These are defective weak spots with potential for propagation of coating breakdown and failure which will cause rust.

A high voltage Holiday Detector works by passing a high voltage through to the conductive substrate to complete the electrical circuit. The holiday detector needs to be adjusted to pass the correct level of current depending on the thickness of the coating. Where the coating has a defect and the circuit is completed, the detector will activate an audible and visual alarm.

Used in accordance with ISO2746, AS3894-1 Standards.

Calculation of Test Voltage

Calculating the correct voltage for your high voltage tester.

calculation of test voltage
1 Coating Factor Coating Type
1 Ultra Hi-Builds

80% + volume solids
e.g Fusion bonded epoxy, solventless epoxy polyester - vinyl ester

2 Hi-Builds 60% to 79% volume solids
e.g High build epoxy, Coal Tar Epoxy
3 Medium Builds 40% to 59% volume solids
e.g. Medium epoxies
4 Low Builds 15% to 39% volume solids
e.g. Vinyl coating, Chlorinated Rubber