A Guide to ASTM B117 for Salt Spray (Fog) Testing ASTM B117 is the internationally recognized standard for conducting salt-spray (fog) tests to evaluate the corrosion resistance of metals, coatings, and surface-treated components. Under this standard, specimens are cleaned, mounted at a slight angle, then placed in a sealed chamber where a neutral sodium-chloride mist (typically 5 % by weight) is continuously sprayed under controlled conditions (about 35 °C, pH 6.5–7.2, high humidity). Over a specified exposure period — from a few hours to thousands — the samples are inspected for rust, pitting, blistering or coating failure. The results provide a comparative measure of durability and help validate protective coatings or surface treatments before real-world deployment. https://www.prestoenviro.com/blogs/guide-to-astm-b117-for-salt-spray-fog-testing