GB/T 9792-2003 specifies the weight method for the determination of the film mass per unit area of the conversion film on metal materials, which is suitable for the conversion film on a variety of metal surfaces, such as phosphoric acid salt film and chromate film. The standard describes in detail the test equipment, specimen requirements, test solution preparation and operation steps, including the weighing, soaking, cleaning and drying of the specimen, and finally calculates the film mass through the weight difference. The standard is proposed by the China Machinery Industry Federation and is centralized by the National Metal and Non-metallic Coating Standardization Technical Committee. It provides a unified technical basis for the mass detection of metal surface preparation to ensure that the mass and performance of the conversion film meet the requirements.