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Corrosion is a pressing issue in metal-based industries wherein components, structures, and other products are developed. The salt spray test has been widely practised to assess coated, uncoated, electroplated, or galvanized metal samples of corrosion resistance. This test tells how a particular material will sustain under extreme environmental conditions over time.

This blog discusses the importance, scientific principles, standard procedures, and key industry applications of the salt spray test. 

What do you mean by a Salt Spray Test?

A salt spray test is one method of accelerating the corrosion of testing methods which demonstrates the influence a saline environment could have on the samples, based on its salts. A sample is carried into a controlled chamber of salt spray and continues its exposure through continuous mist to this saline solution to make it feasible to estimate protective coating efficiency along with determining real conditions.

It is widely applied in industries such as automotive, aerospace, construction, and marine engineering, where the metal components are frequently exposed to moisture and corrosive environments.

Importance of Salt Spray Test

Corrosion may result in structural failure, shortening the product life, and incurring financial losses. The salt spray test allows manufacturers and engineers to determine an accelerated way in which a material can perform well under extreme conditions.

What is a salt spray chamber, and how does it work?

A salt spray chamber is a specialized testing device used to evaluate the corrosion resistance of materials and coatings. It simulates harsh environmental conditions by exposing test samples to a fine mist of saltwater solution. This accelerated corrosion test helps industries like automotive, aerospace, and manufacturing ensure product durability. Complying with international standards like ASTM B117, it plays a crucial role in quality assurance.

Some benefits of the test include:

• Rapid corrosion testing: What might take years under natural conditions is evaluated in days or weeks.

• Quality control: Assures the manufacturer that coatings, plating, or passivation processes are effective.

• Results are standardized: Conducted according to industry standards such as ASTM B117, ASTM G85, and ISO 9227.

• Cost-effective: Saves in the long term due to failures and reduced maintenance costs.

• The salt spray test determines if such a layer endures or breaks with time. It defines passivation as an important concept in corrosion resistance. 

Science Behind the Salt Spray Test

This test is based on electrochemical corrosion principles. The salt solution has particularly aggressive chloride ions that break the protective oxide layer on metals and accelerate corrosion.

Scientific aspects:

• Penetration of chloride ions: The ions penetrate the protective coatings that allow for the oxidation-reduction reactions.

• Electrochemical reaction: The metal will be oxidized, and the corrosion products of iron oxide or rust will therefore be formed.

• Accelerated ageing: The test compresses years of exposure into a controlled environment for days.

Testing can be conducted in different forms:

• Neutral Salt Spray (NSS): It applies a sodium chloride solution with pH 6.5 to 7.2.

• Copper-Accelerated Acetic Acid Salt Spray (CASS): It applies copper chloride dihydrate to make it more aggressive in corrosion.

• Acetic Acid Salt Spray (AASS): Glacial acetic acid is used for the process, lowering pH and increasing its rate.

• The changes are performed according to material and industrial demands for mimicking diverse environmental conditions.

Conducting a Standardized Salt Spray Test (ASTM B117)

The ASTM B117 is the most commonly applied standard for a neutral salt spray test (NSS). The process involves the following major steps:

1. Sample Placement & Chamber Construction

Test specimens are mounted at an angle of 15° to 30° within the cabinet.

The cabinets must be anti-corrosion so as to prevent contamination of the salt fog.

The exposure area is 35°C ± 2°C with relative humidity of 95%.

2. Salt Solution

5 ±1 mass part sodium chloride in 95 mass part demineralized water, is dissolved in it.

Maintain a pH between 6.5-7.2.

Additional solution:

ASTM B368 (CASS Test): Contains 1g of copper chloride dihydrate in 4 liters.

ASTM G85 (AASS Test): Utilizes glacial acetic acid to bring the pH level down to 3.1.

3. Air Supply & Humidifier

Compressed air is filtered out for oil, grease, and dirt.

Air is humidified before entering the chamber to retain constant test conditions.

4. Test Conducting & Interpretation

Sample specimens are exposed under continuous salt fog for a given period.

The test duration depends on material type and industry standards.

Common evaluation methods:

• Mass loss measurement: Determines the material degradation rate.

• White rust formation: Typically seen in zinc coatings (e.g., galvanized samples) within 24 to 96 hours.

• Red rust formation: Observed in iron and steel after approximately 500 hours.

Choosing the Right Salt Spray Chamber

Selecting an appropriate salt spray chamber is crucial for accurate and reliable testing. Key factors to consider include:

• Compatibility with testing standards: The chamber should be compatible with ASTM B117, ASTM G85, ISO 9227, and ASTM B368.

• Corrosion resistant: The chamber should be made of high-grade, durable materials.

• Precise control systems: Automation of pH control and temperature monitoring coupled with regulation of humidity increases the accuracy of testing.

• These salt spray chamber manufacturers feature high-performance equipment with further added features like the following:

• CASS cum salt spray chambers for combined copper-accelerated and neutral salt spray testing.

Why Us?

• Presto salt spray chambers are known for their precision and reliability.

• Customizable options for laboratories and industrial applications.

• When considering a salt spray chamber for sale, it is important to compare features, certifications, and salt spray chamber prices to find the best fit for your testing requirements.

FAQs

1. How long should a salt spray test be conducted?

The duration depends on the material and standard requirements. Common durations include:

24 to 96 hours for zinc coatings (white rust formation).

500+ hours for iron/steel samples (red rust formation).

2. What industries use salt spray testing?

Automotive (coated parts, fasteners)

Aerospace (aircraft components)

Construction (metal structures, railings)

Electronics (corrosion-resistant casings)

3. What is the difference between NSS, CASS, and AASS?

NSS: Neutral Salt Spray: Standard corrosion test by using the solution of NaCl.

CASS: Copper-Accelerated Acetic Acid Salt Spray: The test is more aggressive for decorative coatings.

AASS -Acetic Acid Salt Spray) Using glacial acetic acid enhances the aggressiveness of corrosiveness.

4. What factors are to be tracked while testing?

Temperature ( 35°C±2°C

pH range- varies

Concentration (5±1%) of the salt solution)

Quality of supplied air and amount of humidity 

The most advanced salt spray chambers, in addition to specific solutions such as CASS cum salt spray chambers, help ensure that the manufacturing process meets all industry standards. It can then improve quality assurance processes by looking into Presto salt spray chambers or even just comparing salt spray chamber prices.

For more information on choosing the best salt spray chamber for sale, contact trusted salt spray chamber manufacturers today!

Phone: +91 9210 903 903

Mail: info@prestogroup.com