ASTM B117 Salt Spray (Fog) Testing

Introduction

ASTM B117 Salt Spray Testing is a standardized test method used to evaluate the corrosion resistance of materials and coatings. It involves exposing test specimens to a controlled salt-laden mist or fog environment, typically consisting of a 5% sodium chloride (NaCl) solution at a pH between 6.5 and 7.2 for a specified period. The test determines how effectively a material or coating can resist corrosion over time by simulating a hostile, corrosive environment. This method is widely used in industries such as automotive, aerospace, and coatings to predict the lifespan and durability of products in real-world conditions. 

Scope

The ASTM B117 test method creates and maintains the salt spray (fog) test environment, impacting many industries in 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 valuable information for developing coatings and new materials—industries such as aircraft, transport, paint, infrastructure, and automotive benefit from these tests. The kind of specimens evaluated, the criteria chosen, and the control of the operating factors significantly impact the reproducibility of results in salt spray exposure.

ASTM B117 Salt Spray Test Procedure

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

A humidifying tower with hot and deionized water is provided to create hot and humid air for ASTM B117 testing. This is accomplished by bubbling compressed air through the tower. Then, the salt solution is mixed with hot, moist air at the nozzle, forming a corrosive fog. The relative humidity produced by this fog is 100 %. Finally, the air is blown into the chamber’s exposure zone if lower humidity conditions are desired.

Unless the specifications covering the material or product being tested specify otherwise, the test shall run continuously for the entire test period. The specification of the tested material or product shall designate the exposure period.

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: 

• We remove the specimens carefully. 
• Specimens may be gently washed or dipped in clean running water at 38°C to remove salt deposits from their surface and immediately dried. 
• The specification covering the tested material or product requires careful and immediate examination.

ASTM B117 Specimens

The following are some of the details related to the ASTM B117 standard test:

Conclusion

The conclusion is that ASTM B117 Salt Spray Fog testing has become an essential standard concerning the corrosion resistance of materials and coatings. This test provides exceptional insight into the product’s real-world performance by simulating a harsh salt-laden environment. Its wide use across various industries makes the standard significant in ensuring that materials—from auto parts to aerospace components—last a long time. Furthermore, conformity to such standardized testing allows quality control enhancement, enhances product reliability, and leads to better products being released to the market.

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