GB/T 30648.5-2015 "Paints and varnishes — Determination of resistance to liquids — Part 5: Temperature-gradient oven method" specifies a test method for determining the resistance of single-layer or multi-layer coatings to the action of liquid or paste test media using a temperature-gradient oven, which can clearly indicate the extent of damage caused by the test media to the coating surface and substrate. The test requires a temperature-gradient oven, quantitative pipettes, a drying oven, and a film thickness measuring instrument. After conditioning under standard environmental conditions, the test media are applied to the test panel, which is then placed in the temperature-gradient oven (35°C to 80°C) in close contact with the heating platform. After 30 minutes, the panel is removed and cleaned. Evaluations are conducted immediately and after drying for 24 hours. The results are expressed as the temperature at which a significant change in the coating occurs.