The ASTM D5162-21 standard specifies a method for detecting discontinuities (leakage points) of non-conductive protective coatings on metal substrates. The standard covers two main types of testing equipment: the low-pressure wet sponge method and the high-pressure spark tester. The low-pressure wet sponge method is suitable for coatings with a thickness of less than 0.5 mm, while the high-pressure spark tester is suitable for coatings with a thickness greater than 0.5 mm. The standard emphasizes that the appropriate voltage needs to be selected according to the coating thickness and dielectric strength during testing to avoid damage to the coating. In addition, specific instructions for equipment calibration and operation are provided to ensure the accuracy and reliability of test results. The standard is suitable for detecting minor defects in coatings, such as cracks, holes or impurities, that may significantly reduce the insulation properties of the coating.