The modified salt spray testing is done by ASTM G85 practice that is applicable to metals (non ferrous and ferrous) and coatings (organic and inorganic). The end results are reported as concentration or specific gravity.
ASTM G85 practice is used for modified salt spray (fog) testing. ASTM G85 practice is based on ASTM B117 but it provides more aggressive test parameters like test solution with a lower pH, changing between the neutral and corrosive atmosphere, or a dilute electrolyte mix. ASTM G85 provides five types of salt spray (fog) testing for specification purposes: acetic acid, cyclic acidified, seawater acidified sulphur dioxide, and dilute electrolyte cyclic fog dry test. This practice is useful for nonferrous/ferrous metals, and organic/inorganic coatings.
As defined by ASTM G85, the samples (spaced at about 30 mm) are suspended at a particular angle to the direction of horizontal flow of fog spray via the spray chamber. Severity of the test is increased by increasing the angle of suspension. The samples are sprayed for 24 hrs. At the end of the test, the samples are gently dipped or washed in clean water to remove salt deposits from their surface. Finally, the samples are dried using a stream of clean and compressed air.
The number and type of test sample are defined as per client’s requirement.