Definition - What does ASTM B117 mean?
The ASTM B117 is a standard test carried out to determine the corrosive effect of salt on metallic objects. It is done by spraying salt on a specimen housed in a closed chamber. This is an accelerated form for atmospheric corrosion testing. In this test, the corrosive atmosphere is introduced, allowing the test to be completed in less time than these corrosive processes would naturally occur. This is because conditions in this test are normally harsher than the ones present in the natural environment.
ASTBM B117 is also known as salt spray testing or fog testing.
Corrosionpedia explains ASTM B117
In an ASTM B117 test, a metallic specimen is housed in a controlled chamber, and is sprayed at different angles and locations with a salt solution. The salt (NACl) concentration is usually higher than in the atmosphere and ranges from 3.5-20 percent. The chambers come in different sizes, and designs range from small sizes to walk-in rooms capable of handling large specimens.
A humidifying tower with hot, de-ionized water is used to create hot, humid air. This is achieved by bubbling compressed air through the tower. The salt solution mixes with the hot, humid air at the nozzle and atomizes to form a corrosive fog. The relative humidity created by this fog is 100 percent. When lower humidity conditions are desired, air is blown into the chamber’s exposure zone.
This test might not provide the exact same results as would be produced by similar conditions in the natural environment because of the high concentrations of the corrosive element and the high temperatures, neither of which generally occur in the atmosphere. The ASTM B117 is, however, a valuable test that impacts all industries in terms of quality control. It helps in determining suitable materials for a specific environment and gives useful information that can be used when developing coatings and new materials. The main sectors that benefit from these tests are the aircraft, automotive, transport, infrastructure and paint industries.