corrosion tests

Salt spray test to assess corrosion resistance

July 14, 2025
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Introduction

Metal corrosion is one of the most important challenges facing various industries, costing the global economy billions of dollars annually.  Accelerated corrosion tests, such as salt spray testing, are used to predict the behavior of materials in corrosive environments. Also known as  salt   spray testing, this test is a fast and standardized way to assess the corrosion resistance of coatings and metal materials. In this article, we will review the principles of salt spray testing, and related standards, Equipment needed, its applications and limitations.

1. What is the salt spray test?

The salt spray test is a laboratory method to simulate corrosive conditions in chloride-containing environments (such as coastal areas or salted roads during winter). In this test, metal or painted samples are exposed to salt spraying (sodium chloride solution) and their corrosive behavior is assessed.

1.1. Purpose of the test

  • Assessment of the wear resistance of materials and coatings

  • Quality Control of Metal Products

  • Compare the performance of different coatings

  • Simulation of corrosive environmental conditions in a short time

2. Common standards for salt spray testing

There are different types of standards for this test, the most important of which are:

quality Test Description
ASTM B117 The most commonly used standard for neutral salt spray test (5% sodium chloride solution at 35°C)
ISO 9227 International standard similar to ASTM B117 with additional details
DIN 50021 German Standard for Salt Spray Corrosion Tests
JIS Z 2371 Japanese Standard for Salt Spray Test

3. Equipment for salt spray testing

3.1. Test chamber (salt spray chamber)

  • Body Material: Corrosion resistant (polyethylene, fiberglass or stainless steel)

  • Sprinkler system: special  nozzles to create  uniform salt mist.

  • Heating system: room temperature control between 35 and 50 ° C.

  • Brine tank: storage and pumping of sodium chloride solution

3.2. Saline solution used

  • Standard concentration:   5% sodium   chloride (50 grams of salt per liter of distilled water)

  • Solution pH: Between 6.5 and 7.2 (ASTM B117)

4. Test method

  1. Sample  : preparation

    • Specimens must be clean and free of contamination.

    • If necessary, the edges of the sample are covered with a protective layer.

  2. Placing samples in the  : chamber

    • Specimens are placed at an angle of   15-30 degrees   relative to the vertical.

    • Samples are prevented from contacting each other.

  3. Set test  : conditions

    • Temperature:   35±2°C   (ASTM B117)

    • Spray :    pressure 0.7 to 1.2 bar

    • Test duration:   24 hours to 1000 hours   depending on the type of material

  4. Verify results  :

    • After the test is completed, the samples are washed and dried.

    • The coating is checked for corrosion, rust or bedsores.

5. Salt Spray Test Applications

5.1. Automotive industry

  • Test the strength of the car bodywork, metal parts and paint coating.

5.2. Aerospace, aviation and marine industries

  • Evaluation of the resistance of aluminum alloys, stainless steel and protective coatings.

5.3. Electronic Industries

  • Resistance Test of Printed Circuit Boards and Metal Joints

5.4. Construction industry

  • Resistance Test for Galvanized Coatings and Industrial Paints

6. Advantages and disadvantages of salt spray test

6.1. Benefits

  • High  Speed : Results are obtained in a short time.

  • Relatively  low cost – compared to long-term field trials.

  • Repeatability  : Test conditions are fully controlled.

6.2. Limitations

  • It does not fully  mimic the real environment : corrosion in nature can be affected by other factors such as ultraviolet radiation, variable humidity and pollutants.

  • Error in interpretation of results  : Sometimes the behavior of the material in the salt spray test differs from its actual performance.

7. Compare salt spray test with other corrosion test methods

Test method duration Simulated environment benefits
Salt Spray Test 24-1000 hours Chloride Environments Fast and economical
Intermittent Moisture Test A few weeks or months Moisture alternation and dryness Close to real conditions
Field Test From a few months to a year Natural environmental conditions The most accurate results

8. Conclusion

Salt spray testing is a standard and widespread method for assessing the corrosion resistance of materials and coatings. Despite some limitations, it remains an important quality control tool in various industries due to its high speed and relatively low cost. For more accurate results, it is advisable to combine this test with other corrosion testing methods, such as   periodic   . corrosion testing.

Resources (if needed)

  • ASTM B117 – Standard Practice for the Operation of Salt Mist Devices

  • ISO 9227 – Corrosion Tests in Artificial Atmospheres – Salt Spray Tests

  • Books and articles related to corrosion and surface painting.

This article comprehensively reviews salt spray testing and may be useful for materials engineers, quality control professionals, and researchers.