The standard "ISO 10309-1994 Metal coating porosity test, iron reagent test" specifies the iron reagent test method for determining the porosity of metal coatings. The test is used to evaluate the compactness of metallic coatings, especially in the presence of pores or tiny crazing on the coating surface. The distribution and degree of pores can be detected by the iron reagent test. The standard describes the equipment required for the test, reagent preparation, sample preparation and operation procedures. This method allows to judge the mass and protective performance of coatings and is widely used in metallic coating mass testing, production control and technology development.