ASTM B117 Salt Spray (Fog) Testing

ASTM B117 Salt Spray (Fog) Testing

Scope:

ASTM B117 test method is used to create and maintain the salt spray (fog) test environment that impacts many industries with regard to quality control. The test ASTM B117 is used to compare the corrosive resistance of different metals, determine suitable materials for a specific environment, and determine corrosion creep and coating adhesion. This test provides useful information for developing coatings and new materials. The industries such as aircraft, transport, paint, infrastructure, and automotive benefit from these tests. The kind of specimens evaluated, the evaluation criteria chosen, as well as the control of the operating factors, have a significant impact on the reproducibility of results in salt spray exposure.

ASTM B117 Salt SprayTest procedure:

For the ASTM B117 test, a metallic sample is placed in a controlled chamber. The sample is sprayed at different angles and locations with a salt solution. The salt concentration ranges from 3.5-20 % and usually is higher than that in the atmosphere. The chambers required for handling large samples come in different sizes and designs, ranging from small sizes to walk-in rooms. 

To create hot and humid air for ASTM B117 testing, a humidifying tower with hot and deionized water is provided, which is accomplished by bubbling compressed air via the tower. Then, the salt solution is mixed with hot and humid air at the nozzle, and a corrosive fog is formed. The relative humidity produced by this fog is 100 %. If lower humidity conditions are desired, the air is blown into the chamber’s exposure zone.

Unless otherwise specified in the specifications covering the material or product being tested, the test shall be continuous for the entire duration of the test period. The period of exposure shall be as designated by the specification covering the material or product being tested.

Unless otherwise specified in the specifications covering the material or product being tested, specimens shall be treated as follows at the end of the test: 

• The specimen shall be carefully removed. 
• Specimens may be gently washed or dipped in clean running water not warmer than 38°C to remove salt deposits from their surface and then immediately dried. 
• A careful and immediate examination shall be made as required by the specification covering the material or product being tested.

Sample size:

The number and type of test sample required for ASTM B117 are defined upon mutual agreement between the seller and the purchaser.

Data:

The following data is required for ASTM B117 testing:
Concentration or specific gravity
The pH of the collected solution

Conclusion:

ASTM B117 test method determines the role of salt in enhancing the corrosive resistance of materials in response to salt. The quality and durability check is performed, testing the reliability of various materials for commercial use.