Paints and varnishes - Determination of resistance to filiform corrosion - Part 2: Aluminium substrates (ISO 4623-2:2003); German version EN ISO 4623-2:2004
A scribe mark cut through a coating of paints or varnishes on metal can give rist to various types of corrosion, such as blistering of a coating, corrosion of the metal under the coating as well as filiform corrosion. Filiform corrosion tends to develop under specific conditions of temperature and relative humidity and when traces of acids, bases or salts are present either under the paint coating or at breaks in the coating. These conditions are often found in marine and/or industrial environments. A certain amount of under-creep corrosion of the substrate, starting from the scribe mark, will always occur. Filiform corrosion, however, is considered to be present only if the typical pattern in the form of treads is obvious. This part of ISO 4623 describes a test procedure for assessing the protective action of coatingts of paints or varnishes on aluminium against filiform corrosion arising from a scribe mark cut through the coating. It is only suitable for assessing the performance of the coating/substrate combination tested. It is not suitable for predicting the performance of the coating on different substrates.#,,#