1.1 Purpose
The salt fog Method is performed to determine the effectiveness of protective coatings and finishes on materials. It may also be applied to determine the effects of salt deposits on the physical and electrical aspects of materiel.
1.2 Application
Use this Method for screening purposes only to evaluate the effectiveness and quality of protective coatings and finishes on materiel and material coupons, and to locate potential problem areas, quality control deficiencies, design flaws, etc., in a relatively short period of time. Although not representative of the natural environment (see paragraph 1.3b), this test has been used to provide an indication of potential problem areas associated with the salt (marine) environment. In general, only apply this Method to materiel that will experience significant exposure (as opposed to infrequent or irregular) to high levels of salt in the atmosphere. Use of this Method to evaluate material coupons is not intended to be conducted in lieu of full assemblage testing.
1.3 Limitations
This Method does not attempt to duplicate the complex environment but, rather, it provides a generally stressful situation that may reveal potential problem areas in materiel. Testing in the natural environment, whenever practical, may provide more valuable results. Specifically, this Method does not address:
- a. There is no relationship between this test and any real world exposure duration. The test is not intended to duplicate the effects of a marine atmosphere due to variations in chemical composition and concentrations of the various marine and other corrosive environments.
- b. It has not been demonstrated that a direct relationship exists between salt fog corrosion and corrosion due to other media.
- c. It has not been demonstrated that withstanding the effects of this test guarantees materiel will survive under all corrosive conditions. For acidic atmosphere tests, see Method 518.2. Consult ASTM G85, “Standard Practice for Modified Salt Spray (Fog) Testing” (paragraph 6.1, reference a) for information on introducing a sulfur dioxide environment. Caution: Introducing sulfur dioxide in the salt fog chamber may contaminate the chamber for future salt fog tests.
- d. This test has proven to be generally unreliable for predicting the service life of different materials or coatings.
- e. This test is not a substitute for evaluating corrosion caused by humidity and fungus because their effects differ from salt fog effects and the tests are not interchangeable.