Meaning and Purpose
4.1 Water causes the coating to degrade, so understanding how the coating is waterproof helps to evaluate its performance in practical use. Test failures at 100% relative humidity can be caused by a variety of factors, including defects in the coating itself, contamination of the substrate or inadequate surface treatment. Therefore, this practice is very useful for evaluating the coating individually or the entire coating system.

4.2 Testing at 100% relative humidity for specification acceptance, quality control and research and development of coating and substrate treatment. Some tests are used to determine pass or fail at any time. If there is no evidence of water-related failure after a period of time, the coating system is considered to have passed. Other tests are used to monitor the degree of failure as a function of exposure time.

4.2.1 Arbitrary pass/fail levels and required test durations are typically set in other material specific test methods. Users who do this can use the known performance of the control to set the test endpoint. An alternative is to continue testing until all specimens fail and use the time to failure as a way of distinguishing performance.

4.3 Until the quantitative relevance of the coating or coating system is determined, the results obtained using a 100% humidity test in accordance with this protocol should not be expressed as equivalent to a period of exposure to water in the natural environment.

4.4 The test room may be a small laboratory cabinet or a room large enough to accommodate a car or truck. Some automakers test complete vehicles in a room that maintains 100 percent relative humidity. Corrosion tests can be carried out because the condensed water dripping from the test item will not be recirculated.

ASTM D 2247-2020 “Determination of Water Resistance of Coatings at 100% Relative Humidity”

Scope of
1.1 The practice covers the fundamentals and operating procedures for testing the water resistance of a coating by exposing the coated specimen to an atmosphere maintained at 100% relative humidity in order to form condensation on all surfaces of the specimen.

1.2 This practice uses techniques that create a slight temperature difference within the exposed area in order to form condensation on the coated specimen. When the hotter saturated air passes through the cooler sample, water is deposited on the sample in the form of condensation.

1.3 This practice places the entire specimen in the exposed area, allowing condensation to form on all surfaces. This makes the practice suitable for tablets as well as large or 3D objects. This practice differs from other methods in that only condensation forms on the front coated surface and the back surface is outside the exposed area. Other tests may also deposit water droplets on the surface, but the source is not from condensation (for example, spraying water).

Note 1: Alternative practices for testing paint for water resistance include D870, D1735 and D4585.

1.4 This practice is limited to methods of obtaining, measuring and controlling the conditions and procedures of tests performed at 100% relative humidity. It does not specify specimen preparation or outcome evaluation.

1.5 Values expressed in SI units should be considered standard. The values given in parentheses are for reference only.

ASTM D 2247-2020 “Determination of Water Resistance of Coatings at 100% Relative Humidity”

1.6 This standard is not intended to address all safety issues, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health and environmental practices and to determine the applicability of regulatory restrictions prior to use.

1.7 This international Standard has been developed in accordance with the internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the Committee on Technical Barriers to Trade of the World Trade Organization.