This test is intended for application to components or equipment designed to withstand a salt-laden atmosphere, depending on the chosen severity. Salt can degrade the performance ofparts manufactured using metallic and/or non-metallic materials.The mechanism of salt corrosion on metallic materials is electrochemical, whereas thedegradation effects experienced on non-metallic materials are caused by complex chemicalreactions of the salts with the materials involved. The rate at which corrosive action takesplace is dependent, to a large extent, on the supply of oxygenated salt solution to the surfaceof the test specimen, the temperature of the specimen and the temperature and humidity ofthe environment.Apart from the corrosive effects, this test may be used to indicate deterioration of some non-metallic materials by assimilation of salts. In the following test methods, the period of sprayingwith the relevant salt solution is sufficient to wet the specimen thoroughly. Because thiswetting is repeated after intervals of storage under humid conditions (severities (1) and (2))and in some cases severities ((3) to (6)) supplemented by storage under a standardatmosphere for testing, it goes some way to reproducing the effects of natural environments.Severities (1) and (2) are intended to be used for testing products which are used in a marineenvironment, or in close proximity to the sea. Severity (1) should be used to test productswhich are exposed to the environment for much of their operational life (e.g. ship radar, deckequipment). Severity (2) should be used to test products which may be exposed to the marineenvironment from time to time but will normally be protected by an enclosure (e.g.navigational equipment which will normally be used on the bridge or in a control room).Additionally, severities (1) and (2) are commonly used as a general corrosion test incomponent quality assurance procedures.Severities (3) to (6) are intended for products where, under normal use, there is a frequentchange between salt-laden and dry atmosphere, e.g. automobiles and their parts.Severities (3) to (6), compared to severities (1) and (2), therefore include an additionalstorage under a standard atmosphere for testing.The period of dry atmosphere may happen, in practice, during breaks of operation, e.g. duringthe weekend. This inclusion of such a dry period in severities (3) to (6) leads to corrosionmechanism which can be quite different from those under constant humid conditions.The test is accelerated compared with most service conditions. However, it is not possible toestablish an overall acceleration factor for all kinds of specimens (see IEC 60355).