The **ASTM B117** is a standard test method established by the American Society for Testing and Materials (ASTM) for conducting the **Salt Spray (Fog) Test**. This test is used to evaluate the corrosion resistance of materials, coatings, and painted surfaces. The test involves exposing a test specimen to a controlled environment of salt-laden mist or fog to simulate the effects of natural weathering and saltwater exposure. The primary purpose of the test is to assess the performance and durability of protective coatings, paints, and metal surfaces under corrosive conditions.

During the test, the specimen is placed in a chamber where it's exposed to a continuous cycle of salt spray and drying. The salt spray contains a solution of sodium chloride (NaCl) in water, and the exposure duration and conditions can vary based on the specific requirements of the test being conducted. The corrosion resistance of the material or coating is evaluated by monitoring the progression of corrosion, including the formation of rust, blistering, and other types of degradation.

The results of the ASTM B117 test are often used to compare the performance of different materials or coatings and to predict how they might fare in real-world environments where exposure to salt-laden atmospheres is common, such as coastal or marine environments. It's important to note that while the test provides valuable insights into a material's resistance to corrosion, it's a simulation and may not perfectly replicate all the complexities of actual environmental conditions.

The ASTM B117 standard outlines the specific apparatus, procedures, and evaluation criteria for conducting the salt spray test. It's widely recognized in industries where corrosion resistance is crucial, such as automotive, aerospace, marine, and construction, as a means to ensure the quality and longevity of products.