Currently, a series of harmonized test methods designed to provide information on metal release over time from metallic materials into drinking water are being prepared. When tested in a test rig as described in EN 15664-1 stainless steels show very low metal release rates and the resulting metal concentrations in the water are in most cases below the detection limits of available analytical instruments. The reason for these small metal release rates is the formation of a passive layer on the surface on stainless steels. It was therefore decided to test stainless steels for the properties of the passive layer and not metal release. The material under consideration is tested in an electrochemical test. This test is applied to verify whether the corresponding stainless steel stays passive under the conditions that may be present in drinking water. The test is terminated when the pitting potential of the material or the break-through potential is reached. For verification of the correct performance of the test method, the test is also performed in parallel on material 1.4404 for which the corresponding data are well-known. This standard has been prepared by CEN/TC 164/WG 3 "Effects of materials in contact with drinking water" (secretariat: NEN, Netherlands) under the chairmanship of members of NA 119-04-14 AA "Werkstoffe und Bauteile im Kontakt mit Trinkwasser" ("Materials and products in contact with drinking water") at the Water Practice Standards Committee (NAW).