The dried cathodic electrophoretic coating obtained after drying below 120 ℃ undergoes thermal decomposition to produce low molecular weight compounds (i.e. smoking phenomenon) during the process of further heating to the specified drying temperature to achieve complete solidification, resulting in weight loss of the coating, which is called heating reduction. These low molecular weight compounds turn into oil fume pollution in the drying room, increasing the workload of cleaning and maintaining the drying room, and also increasing the consumption of electrophoretic coatings. So the reduction in heating is also one of the indicators to measure the quality of cathodic electrophoretic coatings. From the perspectives of resource conservation, environmental protection, and reducing the maintenance of drying rooms, the lower the heating reduction of cathodic electrophoretic coatings, the better. The heating reduction of cathodic electrophoretic coatings can be as high as about 10%. In recent years, the heating reduction of cathodic electrophoretic coatings developed is below 4%, and the development trend hopes to reduce it to zero