ASTM B117 is the oldest and most widely used of the salt spray
cabinet test. Purportedly used as early as 1914 with roots in the National
Bureau of Standards, and formalized as an ASTM B117 specification in 1939 by
the American Society for Testing and Materials (ASTM). Early specifications
for this method of Corrosion Testing were subject to much change.
The
Salt Spray (Fog) Test is often used to
evaluate the relative corrosion resistance of coated and uncoated materials
exposed to a salt spray or fog at an elevated temperature. Test specimens
are placed in an enclosed salt spray cabinet or chamber and subjected to a
continuous indirect spray of a neutral (ph 6.5-7.2) salt water solution.
This climate is maintained throughout the duration of the test.
The water used in the salt spray chamber
must be compliant with the ASTM D1193 Specification for Reagent
Water, Type IV; to this is added enough sodium
chloride that a five percent salt solution is
achieved. At the time the specimens are placed into the chamber, the cabinet
should be pre-conditioned to the operating temperature of 35oC
(95oF) and fogging a 5% salt solution at the required of 12ml/hr.
The default position for the sample
placement is at a 15-30 degree angle from the vertical, although,
automotive components are often tested in the "in car" position. Specimens
should be placed in the cabinet so as to avoid any dripping of condensation
from one specimen to another.
Except for the purposes of daily
monitoring collection rates, and for the rotation of test specimens, the
cabinet should remain closed until the test is complete.
Test range in length from 24 to 5000
hours usually in increments of 24 hours.
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