Water can cause the degradation of coatings, so knowledge of how a coating resists water is helpful in predicting its service life. Failure in water fog tests may be caused by a number of factors, including a deficiency in the coating itself, contamination of the substrate, or inadequate surface preparation. The test is therefore useful for evaluating coatings alone or complete coating systems.

Water fog tests are used for research and development of coatings and substrate treatments, specification acceptance, and quality control in manufacturing. These tests usually result in a pass or fail determination, but the degree of failure may also be measured. A coating system is considered to pass if there is no evidence of water-related failure after a specified period of time.

Results obtained from the use of water fog tests in accordance with this practice should not be represented as being equivalent to a period of exposure to water in the natural environment, until the degree of quantitative correlation has been established for the coating or coating system.

The test apparatus is similar to that used in Practice B 117, and the conversion of the apparatus from salt spray to water fog testing is feasible. Care should be taken to remove all traces of the salt from the cabinet and reservoir when converting from salt spray to water fog testing.

1.1 This practice covers the basic principles and operating procedures for testing water resistance of coatings in an apparatus similar to that used for salt spray testing.

1.2 This practice is limited to the methods of obtaining, measuring, and controlling the conditions and procedures of water fog tests. It does not specify specimen preparation, specific test conditions, or evaluation of results.

Note 1—Alternative practices for testing the water resistance of coatings include Practices D 870, D 2247, and D 4585.

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

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.