ISO 8502-15 is part of the surface cleanliness assessment test for steel surface preparation before painting. This part is the extraction of soluble contaminants for acid extraction analysis. The standard specifies methods for the extraction and determination of soluble contaminants on the surface of steel to assess the cleanliness of the steel surface. The standard specifies the preparation of the extraction solution, the conditions and time of extraction, etc. Specifically, the standard requires the extraction of the steel surface under specific conditions, followed by measurement of the concentration of soluble contaminants in the extraction solution to evaluate the cleanliness of the steel surface. The standard also specifies the accuracy and Reliability requirements for the extraction and determination, as well as the manner in which the test results are reported. The standard applies to a wide range of steel surfaces, including automotive parts, building structures and Machinery, among others. By following this standard, accurate, reliable and comparable steel surface cleanliness test results can be obtained to ensure paint mass and performance.