What occurs if the voltage on a spark tester exceeds the dielectric strength of a coating?

When the voltage on a spark tester exceeds the dielectric strength of a coating, the outcome is that a hole is effectively blown in the coating. This phenomenon occurs because dielectric strength refers to the maximum electric field a material can withstand without experiencing failure or breakdown. If the applied voltage surpasses this threshold, it can cause the material to ionize, resulting in a breakdown of the coating’s structure which may manifest as a crater or perforation.

This breakdown can result in loss of protective properties of the coating, leading to potential exposure of the underlying substrate to corrosive environments, thus compromising the integrity of the component being tested. Therefore, it's essential for inspectors to understand the importance of dielectric strength and to ensure that testing does not exceed these critical voltage limits to maintain the effectiveness of protective coatings.