The standard DIN EN ISO 15721-2001 Metallic platings porosity test, Porosity of gold or palladium platings by sulfuric acid/sulfur dioxide vapor "specifies a method of testing the porosity of gold or palladium platings by exposing them to sulfuric acid and sulfur dioxide vapor environment. Porosity is an important indicator of coating sealing and corrosion resistance. This method assesses the presence and number of surface pores of metallic coatings by observing changes in their surface under specific conditions, which indirectly reflects the mass and protective capacity of the coating. This standard provides a reliable technical basis for the performance testing of metal platings and is widely used in the quality control and evaluation of metallic coating products.