GB/T 7991.6-2025 "Test methods for vitreous and porcelain enamel - Part 6: High voltage test" is a key standard for evaluating the insulation integrity of vitreous enamel products (such as coatings on the inner walls of chemical equipment). This method involves applying a high voltage of not less than 2 kV (direct or alternating current) to the vitreous enamel layer and detecting whether current passes through, thereby identifying defects such as micro-pores and cracks in the coating. The standard applies to vitreous enamel layers with a thickness of not less than 500 micrometers, and specifies clear requirements for core parameters such as the output voltage and short-circuit current of the high-voltage generator used in the test. This method provides an important basis for the safe operation of equipment and quality control.