This International Standard specifies equipment and a method for using nitric acid vapour to determine porosity in gold coatings, particularly electrodeposits and clad metals used on electrical contacts. This method is designed to show whether the porosity level is less than or greater than some value that, by experience, is considered by the user to be acceptable for the intended application. It is suitable for inlays or claddings containing 75 % or more of gold, for electrodeposits containing 95 % or more of gold or for substrates of copper, nickel and their alloys that are commonly used in electrical contacts. The nitric acid vapour test is too severe to be used for gold coatings less than 0,6 μm thick. It is also not suitable for coatings that are less noble than gold or platinum, such as palladium and its alloys, or gold-flashed palladium and its alloys. Several other porosity testing methods are described in ISO 10308 and in the literature (see e.g. Bibliography, [1] and [2]).