This International Standard specifies a test method for measurements over extended time periods of the open-circuit potential of implant materials and surgically implantable devices immersed in a test environment related to body fluid, using a standard corrosion test cell to study the electrochemical corrosion properties of the devices. This method of monitoring the open-circuit potential can also be combined with mechanical static or dynamic loading tests. This International Standard is applicable in particular to metallic materials which form passive layers with protective properties against corrosion, as typical for surgical implant materials. This test method is intended for the investigation of single metallic materials or alloys. It is not applicable to dissimilar material combinations, which require particular considerations in measuring and interpreting the results.