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 of parts manufactured using metallic and/or non-metallic materials. The mechanism of salt corrosion in metallic materials is electrochemical whereas the degradation effects experienced on non-metallic materials are caused by complex chemical reactions of the salts with the materials involved. The rate at which corrosive action takes place is dependent to a large extent on the supply of oxygenated salt solution to the surface of the test specimen the temperature of the specimen and the temperature and humidity of the 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 spraying with the relevant salt solution is sufficient to wet the specimen thoroughly. Because this wetting 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 standard atmosphere 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 marine environment or in close proximity to the sea. Severity (1) shall be used to test products which are exposed to the environment for much of their operational life (e.g. ship radar, deck equipment). Severity (2) shall be used to test products which may be exposed to the marine environment 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 in component quality assurance procedures.
Severities (3) to (6) are intended for products where under normal use there is a frequent change 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 additional storage under a standard atmosphere for testing.
The period of dry atmosphere may happen in practice during breaks of operation e.g. during the weekend. This inclusion of such a dry period in severities (3) to (6) leads to corrosion mechanism 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 to establish an overall acceleration factor for all kinds of specimen (see IEC 60355: 1971).
2 Normative References
The following documents are indispensable for the application of this Standard. For dated references, only the dated edition is applicable to this Document. For undated references, the latest edition (including all the amendments) applies.
GB/T 2421.1—2008 Environmental Testing - General and Guidance (IEC 60068-1: 1988, IDT)
GB/T 2423.3—2006 Environmental Testing for Electric and Electronic Products - Part 2: Testing Methods - Test Cab: Damp Heat Steady State (IEC 60068-2-78: 2001, IDT)
IEC 60355: 1971 An Appraisal of The Problems of Accelerated Testing for Atmospheric Corrosion
3 General Description of the Test
For severities (1) and (2) the test procedure is separated into a specified number of periods of spraying by a salt mist at a temperature between 15℃ and 5℃, each followed by a storage period under humid conditions at (40±2)℃, (93±3)% relative humidity.
For severities (3), (4), (5), (6), the test procedure is separated into a specified number of test cycles. Each test cycle consists of four periods of spraying by a salt mist at a temperature between 15℃ and 35℃, each immediately followed by a storage period under humid conditions at (40±2)℃, (93±3)% relative humidity, and of one storage period under a standard atmosphere for testing at (23±2) ℃ and 45 % to 55 % relative humidity after these four periods of spraying and storage under humid conditions.
If the spray period and storage period are carried out in different chambers, care shall be taken to avoid loss of salt solution deposits on the specimen and to avoid any damage to the specimen due to handling.
The specimen is never energized during the spray period, and not normally during the storage period.
