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MIL-STD 810 Acidic Atmosphere Testing

The acidic atmosphere test helps determine the resistance of materials and protective coatings to corrosive atmospheres. It also helps determine its effect on operational capabilities. Method 518 is best for material that is likely to be stored or operated in acidic atmospheres.

The corrosive atmosphere test  is not a replacement for the salt fog method. It is not suitable for evaluating the effects of hydrogen sulfide that oxidizes to form sulfur dioxide. Acidic atmosphere testing labs should be equipped with salt fog chambers for this test. However, introducing an acidic or sulfur dioxide atmosphere in a salt fog chamber may contaminate the chamber for future tests.

Keystone Compliance has a fully equipped corrosion lab. Our test engineers have an in-depth knowledge of corrosion testing for commercial, military, and aerospace products. This knowledge is drawn from MIL-810 acidic atmosphere section, but includes MIL-810G acidic atmosphere and MIL-810H acidic atmosphere. .

The following information is extremely technical in nature. It provides a summary of MIL STD-810, Method 504.3. It applies previous versions of the standard. This includes MIL-STD 810G acidic atmosphere and MIL-STD 810H acidic atmosphere.

What are the Effects of an Acidic Environment?

Acidic atmospheres are of concern for material in the vicinity of industrial areas or near the exhausts of fuel burning devices. In acidic atmospheres chemical can attack surface finishes and non-metallic materials. These environments may also cause corrosion of materials and pitting of cement and optics.

These are  examples of a few problems that could occur as a result of acidic atmosphere exposure. It is important to note that all testing should be done by certified engineers in a fully equipped acidic atmosphere laboratory.

How Do You Determine the Sequence for the Best Acidic Atmosphere Testing?

Use the anticipated life cycle sequence of events as a general sequence guide. There are at least two philosophies related to the solvents resistance test sequence. One approach is to conserve test item life by applying what are perceived to be the least damaging environments first. For this approach, generally apply the acidic atmosphere test late in the test sequence.

Another approach is to apply environments to maximize the likelihood of disclosing synergetic effects. For this approach, consider acidic atmosphere testing following dynamic tests, such as Acidic Atmosphere and shock. Perform acidic atmosphere testing after any humidity or fungus testing. Perform it before any sand and dust testing or other tests that damage protective coatings.

Sand and dust testing deposits may inhibit acid effects as well as abrade protective coatings. Acid deposits may inhibit mold/fungal growth. Residual deposits may accelerate chemical reactions during humidity testing. Because this test is similar in severity to the salt fog test, separate test items should be used for each.

What are the Proper Test Levels and Acidic Atmosphere Lab Conditions?

Select this method and relevant procedures based on the test item’s requirements documents and the tailoring process. Having done that, identify the appropriate parameter levels and applicable test conditions and techniques for these procedures. Base these selections on the requirements documents, the Life Cycle Environmental Profile (LCEP), and information provided with this procedure. Consider essential parameters like exposure temperature, exposure time, test item configuration, chemical composition of test atmosphere, and concentration of test solution.

What is the Proper Test Duration?

Due to the complexity of naturally occurring corrosion processes, there are no strict equivalencies with real exposure. There are two potential severity levels of test duration. First is three 2-hour spraying periods with 22 hours storage after each. Use this severity for simulating infrequent periods of exposure, or for exposure in areas of much lower acidity.

Second is four 2-hour spraying periods with 7 days storage after each. Use this severity to represent approximately 10 years natural exposure in a moist, highly industrial area. Or use it to represent a shorter time in close proximity to vehicle exhaust systems.

What is the Best configuration for the Test Item?

The configuration of the material is an important factor in how an acidic atmosphere affects it. Therefore, during the test use the anticipated configuration of the material during storage or use. As a minimum, consider the following configurations:

  • In a shipping/storage container or transit case.
  • Protected or unprotected.
  • Deployed (realistically or with restraints, such as with openings that are normally covered).
  • Modified with kits for special applications.

What Information is Required to Conduct Atmosphere Tests Adequately?

Pretest

Before testing the item make sure to visually and functionally examine the proper areas of it. Know the inclusion or exclusion of these areas during testing.

For the test itself you must know whether it is a demonstration of performance or of survival. This will clarify if the test is meant to demonstrate safety, safety and performance, or resistance to chemical attack. To assess functional performance, the phases during testing, when the test item is to function and be assessed must be known. And the levels of performance are required.

During Testing

During contamination testing there are a few important actions that must be taken. A record of chamber temperature versus time conditions must be kept. Technicians must observe fallout quantities per unit of time, as well as fallout pH.

Post-Test

After the test, engineers should re-examine areas of the test item visually and functionally, and explain their inclusion or exclusion. Test variable, test solution pH, and test solution fallout rate should be noted. Fallout rate can be measured in ml, cm squared, or hours.

Results of examination for corrosion, electrical, and physical effects should be reported. Additionally, any observations to aid in failure analysis should be recorded. A note should also be made of any deviation from the original test plan that occurred.

Who Should I Trust to Get Acidic Atmosphere Certification for My Products?

Keystone Compliance has been recognized as one of the best acidic atmosphere labs in the country. We employ the best test engineers, provided with high quality equipment. Keystone provides acidic atmosphere compliance testing certifications for commercial, military, and aerospace products. Contact us to learn why so many manufacturers rely on Keystone Compliance to meet their compliance testing needs.

There have been several versions of acidic atmosphere testing procedures in MIL-STD-810 Acidic Atmosphere testing. Below is a list of each version and the appropriate method number: