ASTM B117 Standards: Guide to Operate Salt Spray (Fog) Test Apparatus

Salt spray testing is among the most critical methods to estimate the corrosion resistance of surface treatments, coatings, and metals, and guarantee the durability of products. All the Testronix Instruments adhere strictly to ASTM B117, the globally recognized salt spray (fog) testing standard. The standardized test is performed in a controlled environment to determine the material's corrosion resistance and is frequently employed in the automobile, aerospace, and manufacturing sectors.

With the help of standards of ASTM, manufacturers like us provide accurate and stable test results, allowing our customers to enhance product quality, extend lifespan, and guarantee conformity to industry standards.

What is ASTM B117 Standards for Salt Spray Test

ASTM refers to the American Society for Testing and Materials, which provides standard practice for environmental and engineering services. The ASTM B117 is one of the most common standards for the salt spray test that defines certain parameters and specifications to perform the salt spray test in specific environmental conditions. This standard practice for operating salt spray apparatus must be followed by various industries, including –

• Aerospace and aircraft
• Automotive manufacturing
• Construction and building materials
• Infrastructure, such as water and sewer pipes

ASTM B117 is not restricted to salt spray operations only but also outlines the best practices for apparatus requirements, types and preparation of test specimens, temperature conditions, the timeline of the exposure period, etc.

Purpose of ASTM B117 for Salt Spray Test

The ASTM B117 standard is designed to ensure the material’s durability and to test how well the material resists corrosion when exposed to salt water. Here, B is referred to as “Non-ferrous materials,” and 117 is an “assigned sequential number.”

It is a detailed and standardized document with various parameters and guidance, including the following:

• Gauge the corrosion resistance of metals and protective coatings.
• Provide a proportional analysis of different materials.
• Certify coatings meet industry specifications for corrosion resistance.
• Categorize defects in coatings such as cracks, pinholes, and adhesion failures.

It is important to note that ASTM B117 does not predict real-world corrosion performance. It provides a standardized environment for comparing materials under accelerated/stimulated conditions.

Standard Practice for Operating Salt Spray (Fog) Apparatus

Standard practice for salt spray testing is utilized to generate consistent and reproducible results. It provides detailed guidelines for the apparatus to be used, how testing is to be conducted, and how the conditions should be controlled to mimic the required environment during salt spray testing. Here is the detailed standard practice for operating salt spray fog apparatus –

Scope of Standard Practice

The scope of ASTM B117 standard practice in various industries regarding the operation and testing procedure of salt spray test. The standards work as the guidelines for the technicians or operators that include the following important clauses –

1.1 This practice describes the apparatus details, procedure, and conditions for creating and sustaining the salt spray (fog) test environment.

1.2 This practice does not feature the test specimen shape or exposure times to be used for a specific product or the interpretation to be placed on the results.

1.3 The values in SI units are to be regarded as standard. The values in parentheses are for information purposes only.

1.4 This standard does not significantly cover all of the safety concerns, if any, associated with its use.

Preparation and Position of Test Specimen

To perform the test accurately and as per the ASTM standards, the preparation and positioning of the test specimen is critical. The following are the important clauses of standard practice to be followed while using the specimen as per the ASTM B117 standard –

• The test specimen is the core ASTM guidelines that include the type and number of test specimens to be used.
• Specimen should be cleaned properly however, the cleaning method is optional depending on the nature of the surface and contaminants.
• Specimens coated with paints or non-metallic coatings shall not be cleaned or handled excessively before the test.
• Unless otherwise specified, the cut edges of the plate shall be protected with a suitable coating.
• Unless specified, the position of the specimen should be 15 to 30⁰ vertically or to the principle direction of flow of fog.

Setting Up Salt Spray Chamber

Once the specimen is positioned, the next crucial step is to set up the salt spray chamber which is the core of the entire standard practice. B117 describes how to set up the apparatus and what are the steps to be followed for accuracy –

• Place the apparatus in a properly ventilated room, not exposed to direct sunlight or temperature changes.
• Check the chamber for leaks or blockages that can affect the diffusion of the fog.
• Set the chamber temperature, typically between 35°C (+/-2) or 95°F. Humidity and salt levels should be controlled as well.

Preparation Salt Solution

The salt solution shall be prepared by dissolving 5 (+/-1) parts by mass of sodium chloride in 95 parts of water conforming to Type IV water. Here are the comprehensive steps to be taken as per the ASTM B117 standard –

• The salt should be sodium chloride, with careful attention that it shouldn’t be more than 0.3% of total impurities.
• Halides shouldn’t be more than 0.1% by mass.
• Copper content should be less than 0.1% ppm by mass.
• The PH level of the salt solution should range from 6.5 to 7.2, providing the condition of atomization at 35⁰.

Test Monitoring

Test monitoring is the internal function of salt spray testing and ASTM B117 comprehensively documented how to monitor the test and results. Here are a few standard practices to be followed by operators –

• The test duration depends on the material and purpose of the test, which is typically run from 24 to 1000 hours.
• During monitoring, make sure that the test is as per the specified temperature, humidity, and environmental conditions.

 Maintenance of Equipment

In various conditions; continuous uses of apparatus, the equipment may not deliver accurate results, so maintenance is paramount before testing. The following are the guidelines outlined by ASTM standards –

• It should be ensured that salt spray test equipment must be cleaned properly before and after the completion of the test.
• The calibration of testing equipment must be done on a regular basis to get reliable and accurate results.
• If test results are not desirable and inconsistent, replace the equipment, especially in case of wear, corrosion, and breakdown.

Quick Summarization Standard Practice –

• Test Solution – Should consist of 5% NaCl (by weight)
• Temperature Range – 35°C - 50⁰C (95.0°F – 122.0°F)
• Spray Conditions – 1.0 – 2.0 ml per hour per 80 cm
• PH Control – 6.5 to 7.2
• Test Duration – 24 hours to 1000 hours

Advantages of ASTM B117 for Salt Spray Test

ASTM B117 standard is a vital guideline for operators who indulge in salt spray testing. Apart from accurate results, following the ASTM standard practices comes with below-mentioned advantages –

• Standardized & Repeatable – Ensures consistent and comparable results across industries.
• Accelerated Corrosion Testing – Provides quick insights into corrosion resistance.
• Cost-Effective – Helps manufacturers identify material weaknesses before real-world application
• Applicable to Various Coatings – Suitable for paints, electroplated coatings, anodized layers, and more.

Limitations of ASTM B117

ASTM B117 is used in various industries and is the most followed ASTM standard for accurate and reliable results but it has some limitations as follows –

Does Not Imitate Realistic Scenarios – The test accelerates corrosion but fails to accurately reproduce realistic scenarios like exposure to the sun, humidity fluctuations, or contamination.

Does Not Simulate All Types of Environment – Even though ASTM B117 standards are heavily used in various industries, they lack to simulate specific environmental conditions like acidic, alkaline, and UV radiations.

Too Aggressive on Some Materials – Some coatings pass the test but others do not as they overly perform in actual service conditions with some materials.

Alternatives of ASTM B117 for Salt Spray Test

Even though ASTM B117 is the most used and standardized guideline for salt spray tests and other test procedures, the following standards are often used –

• ASTM G85 – Modified salt spray (fog) test with cyclic exposure
• ISO 9227 – International standard for salt spray testing
• ASTM D5894 – Cyclic salt fog and UV exposure test
• ASTM G44 – Crevice corrosion testing in seawater
• ASTM B368 – Test method for copper-accelerated acetic acid-salt spray (fog) test (CASS Test)

Conclusion

Industries that frequently conduct Salt Spray Tests or utilize salt spray (fog) apparatus must align the best practices outlined by ASTM B117 and other critical standards. With standard practices, including proper sample preparation, solution preparation, chamber calibration, and regular maintenance, industries can achieve consistent and reproducible results.

Testronix Instruments follows standard practices for operating salt spray (fog) apparatus, and all our products align with ASTM standards, including B117. Industries can trust our high-quality equipment, including salt spray testing, to get reliable and precise results. For more information, Contact Us or Get a quote.