Introducing ASTM B117 - Industrial Physics
ASTM B117 is the global ASTM international standard test method to follow when operating salt spray (fog) apparatus.
The American Society of Testing and Materials (ASTM) test B117 is one of the most widely adopted standards for salt spray testing. It’s followed all over the world. Its provisions are frequently re-written into the national standards of other countries and appear in other industry specific corrosion test standards.
This ASTM standard can be used to inspect the relative corrosion resistance of coated and uncoated metallic specimens, when exposed to a salt spray testing climate at an elevated temperature.
Over time corrosion causes oxides in the form of white rust and red rust to appear. The duration of the ASTM B117 test depends on the corrosion resistance of the coating. You tend to find that the more corrosion resistant the coating is, the longer the period of salt spray testing before any oxides appear.
ASTM B117 was developed in accordance with internationally recognized principles on standardization. These salt spray testing principles were established in the ‘decision on principles for the development of international standards, guides and recommendations issued by the World Trade Organization ‘technical barriers to trade (TBT) committee.’
The ASTM B117 salt spray testing process
This ASTM standard covers the apparatus, procedure, and conditions required to create and maintain the salt spray (fog) test environment. However, ASTM B117 doesn’t define the type of test specimen or exposure periods to be used for a specific product, nor the interpretation to be given to the results.
Salt spray testing is performed by placing samples in an enclosed test chamber designed in accordance with ASTM B117. Your samples are exposed to a continuous indirect spray of salt water solution, which is referred to as fog or mist.
The salt spray testing solution is prepared by dissolving pure sodium chloride into pure water, in a ratio of 5% sodium chloride to 95% water, by weight. This hits the specimens at a rate of 1.0 to 2.0 ml/80cm²/hour, in a chamber temperature of +35C.
The pH of the salt solution fall-out for ASTM B117 testing is maintained at a neutral pH of between pH 6.5 and 7.2. Within the industry this is known as Neutral Salt Spray (NSS).
ASTM B117 salt spray testing equipment
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