ASTM-D2247:15(R2020) pdf free download – Standard Practice for Testing Water Resistance of Coatings in 100 % Relative Humidity.
3. Summary of Practice
3.1 Coated specimens are placed in an enclosed chamber containing a heated, saturated mixture of air and water vapor. The temperature of the chamber is usually maintained at 38°C (100°F). At 100 % relative humidity (RH), a very small temperature difference between the specimen and the surrounding vapor causes the formation of condensation on the specimens. The exposure condition is varied by selecting the duration of the test. Water permeates the coating at rates that arc dependent upon the characteristics of the coating. Any effects such as color change. blistering, loss of adhesion, softening. or embrittlement are observed and reported.
4. Significance and Use
4.1 Water can cause the degradation of coatings. so knowledge of how a coating resists water is helpful for assessing how it will perform in actual service. Failure in tests at 100 % relative humidity may be caused by a number of factors including a deficiency in the coating itself, contamination of the substrate, or inadequate surface preparation. This practice is therefore useful for evaluating coatings alone or complete coating systems.
4.2 Tests at 100 % relative humidity are used for specification acceptance, quality control, and research and development for coatings and substrate treatments. Some tests are used for a pass or fail determination at an arbitrary time. A coating system is considered to pass if there is no evidence of water-related failure after a period of time. Other tests are used to monitor degree of failure as a function of exposure time.
4.2.1 Arbitrary pass/fail levels and the test durations required are typically set in other material specific test methods. Users of this practice alone may use the known performance of the controls to set test end points. Another option is to continue the test until all specimens have failed, and use the time to reach failure as a way to differentiate performance.
4.3 Results obtained from the use of 100 % humidity 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.
4.4 The test chamber can be a small laboratory cabinet or a room large enough to hold an automobile or a truck. Some automobile manufacturers test completed vehicles in rooms maintained at 100 % relative humidity. Corrosion tests can he conducted, as the condensate dripping off the test articles in not recirculated.
5. Apparatus
5. 1 Test Chamber, constructed of corrosion-resistant materials with supports br the test specimens.
5.2 Source of Heated Water Vapor can be created by one of the following methods:
5.2.1 Heated Water Tank, within the test chamber, a water supply, and a water level control.