This part of ISO 9022 specifies methods for the testing of optical instruments and instruments containing optical components, under equivalent conditions, for their ability to resist salt mist. Exposure to salt mist mainly results in the corrosion of metals; effects may also occur by way of clogging or binding of moving parts. The purpose of testing is to assess as early as possible the ability of the instrument, and particularly of the surfaces and protective coatings of the instrument, to resist the effects of a salt atmosphere. Normally, representative samples or complete small units are used for testing. Complete large instruments or assemblies are only tested as specified in this part of ISO 9022 in exceptional cases.