Definition - What does Salt Fog mean?
Salt fog is a type of accelerated corrosion test that is performed to assess the comparative corrosion resistance of certain materials when exposed to salt fog or salt spray at increased temperature levels.
In this test, specimens are put inside a chamber or cabinet for salt fog testing, with constant salt water spray or indirect fog, while the climate is maintained during the test.
Salt fog is also known as the fog test or salt spray test.
Corrosionpedia explains Salt Fog
The salt fog test is widely used since it is repeatable and consistent. It is commonly applied in various industries such as the following:
The test is highly beneficial in corrosion resistance evaluation of finished surfaces, equipment parts and more. This test is also one of the best ways to examine the permeability of seals and coatings. Such coatings are used to provide metallic parts with adequate protection against corrosion. The most common type of coatings that this test can evaluate include:
- Organic coatings, phosphates and painted metals
- Electroplated chromium zinc, zinc alloy, copper, tin and nickel
- Non-electronic coatings like zinc flakes
- Painted surfaces subjected to hot-dip galvanized coatings
This is a very cost effective technique that is usually performed in an enclosed chamber. The sample is exposed to salt fog, which is very corrosive in nature. The period of exposure to salt fog is identified by the existing standards and coating type. Normally, this test lasts for about 72 hours, but it can be longer or shorter depending on the existing conditions. After the assigned period, element experts inspect the sample and assess its resistance to corrosion by identifying the existence of oxides.