What is ASTM B117

The ASTM B117 standard is a globally established benchmark for salt spray corrosion testing. Its methodology has been extensively adopted worldwide and forms the basis of many national and sector-specific corrosion test specifications.

Test Conditions

The test involves placing specimens in an enclosed chamber where they are exposed to a continuous indirect neutral saline water, producing a fine fog or mist. The fallout rate is controlled between 1.0 and 2.0 ml per 80 cm² per hour, with the chamber temperature maintained at + 35°C. In addition to this the pH of the fallout must be within the range of 6.5 to 7.2.  Chamber conditions are held at a constant steady state for the duration of the test, which can be varied as required.

Method of testing

Salt spray testing is carried out by exposing test samples within a corrosion chamber that complies with the design requirements of ASTM B117 and is operated under the conditions prescribed by the standard. The salt spray  is produced from a solution containing 5% sodium chloride and 95% water by weight. Both the salt and water used in preparing the solution must satisfy the purity requirements specified in ASTM B117, for example the water quality must be of Type IV Water from D1193, which has a stricter limit on conductivity compared to ISO 9227. Prior to the introduction of the test specimens, the chamber is brought to the required operating temperature of 35°C and adjusted to achieve the correct salt spray collection rate.

Verification of the salt fog fallout rate is undertaken by the use of a minimum 2x 80cm2 funnel per atomiser, the funnel discharges into a graduated cylinder in which the solution can be measured. The collectors are installed within the chamber at approximately the same level as the test specimens. In accordance with ASTM B117, one collector is positioned near the atomiser and another at a more distant location. Their exact placement must also take account of the chamber manufacturer’s defined test area to ensure representative measurement of salt fog fallout throughout the working space.

Typical Application of ASTM B117 Testing

Typical application of ASTM B117 tends to be in the following sectors:

• Automotive
• Aerospace & Defence
• Marine and Offshore