One non-destructive test method used on protective coatings to find unacceptable discontinuities like pinholes and voids is the holiday test or continuity test.The test means analyzing an electrical circuit to determine whether current flows to complete the circuit. Applying low voltage (connected in series with an LED or sound device like a piezoelectric speaker) across the selected path is how you conduct a holiday test or continuity test. The test area is considered to be conductive if the electrical flow is found, which detects the presence of discontinuities like pinholes and voids.
This test is commonly utilized in offshore companies where nonconductor coatings are needed to protect piping and structures .Holiday (Continuity) testing method instruction is provided to EIWAA Gulf rock experts in accordance with AS 3894.1, ASTM G62, and similar national and international standards.
Wet Sponge Holiday Testing Method: On conductive surfaces, this holiday testing technique is used to test insulating coatings that are less than 20 mils (500 microns) thick. The voltage ranges from 5 volts to 120 volts, and it exclusively detects pinholes.Small holes that extend all the way to the substrate are called pinholes. Through capillary action—liquid flowing through narrow spaces defying gravity—they function like a capillary tube, sucking moisture down to the steel substrate and speeding up the corrosion process. Capillary motion is also at play in the wet sponge method for finding pinholes and the water is drawn through the holes by capillary action when a moist sponge is steadily passed over the covered surface, and when it contacts the bare substrate, it completes the process.
High Voltage holiday Test: Instead of using low voltage with a sponge, the high voltage holiday detection method applies high voltage to a metal probe that is passed over the coated surface.The actual voltage used will depend on the thickness and dielectric strength of the coating being tested, as well as the test method or standard you’re using. Generally speaking, the voltage should be high enough to cover the gap between the probe and the substrate in regions where the coating is electrically weaker due to a flaw.An alert will sound to let you know a flaw has been located when any hole or weakness is found since the current will flow through the substrate and back into the device via a grounding connection.
Other Painting Inspection service includes but not limited to,
- Salt contamination test
- Dust level test
- Surface profile check
- DFT Evaluation
- Wet film thickness measurement
- Cross hatch adhesion Test
- Peel Test
- Pull off Adhesion Test
- Painting Inspection and Certification
- Painting defect evaluation
- Blasting Grade Evaluation
Painting Inspector is certified by NACE Level II/CSWIP B Gas Gr.2 Inspectors to conduct paining inspection and certification of marine and industrial equipment’s.