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Paint and Coatings Industry Standards
D870 Standard Practice for Testing Water Resistance of Coatings Using Water Immersion
Immersion in water can cause the degradation of coatings. Knowledge on how a coating resists water immersion is helpful in predicting its service life. Failure in a water immersion test 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 immersion tests are used for research and development of coatings and substrate treatments, specification acceptance, and quality control in manufacturing. These tests typically 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 water immersion 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.
Corrosion tests of a scribed coating on a ferrous substrate are impractical in water immersion tests as the corrosion products tend to contaminate the water bath. Continuous overflow of the test tank is sometimes required to maintain consistent water quality.
The apparatus for the test is relatively inexpensive and can be as simple as a glass beaker with a stirrer. It is also possible to use very large tanks for testing coated pipe or other large coated products.
