GB/T 9989.4-2015 Measurement of alkali erosion resistance of focused enamel solution. This is the fourth part of the standard, which stipulates that the test is carried out in a cylindrical container. The standard specifies the test equipment, such as a specific cylindrical container, describes the sample preparation and test operation procedures, places the enamel sample in the alkali solution, observes the erosion under the specified conditions, and gives the result evaluation method. With this method, the corrosion resistance performance of enamel in the alkaline environment can be accurately evaluated, providing the testing basis for the production and Application of enamel products, and helping to ensure the performance and life of the product under alkaline conditions.