Meaning and Purpose
4.1 Immersion in water can cause degradation of the coating. Understanding how a coating resists water immersion can help predict its service life. A water immersion test failure can be caused by a variety of factors, including defects in the coating itself, contamination of the substrate, or inadequate surface treatment. Therefore, the test can be used to evaluate individual coatings or complete coating systems.

4.2 Water immersion testing is used for coating and substrate treatment research and development, specification acceptance, and quality control in manufacturing. These tests typically lead to a determination of pass or failure, but can also measure the extent of failure. If there is no evidence of water-related failure after a specified time period, the coating system is considered to have passed.

4.3 Until the quantitative relevance of the coating or coating system is determined, the results obtained from water immersion tests performed in accordance with this protocol should not be expressed as equivalent to a period of exposure to water in the natural environment.

ASTM D 870-2020 Determination of Water Resistance of Coatings by Immersion Method

4.4 In water immersion testing, it is impractical to perform corrosion tests on scribe coatings on ferrous metal substrates because corrosion products tend to contaminate the water bath. It is sometimes necessary to test the continuous overflow of the tank to maintain consistent water quality.

4.5 The equipment used for testing is relatively inexpensive and can be as simple as a glass beaker with a stirrer. Very large tanks can also be used to test coated tubes or other large coated products.

Scope of
1.1 The practice covers the fundamentals and operating procedures for testing the water resistance of a coating by immersing part or all of the coated specimen in distilled or softened water at room temperature or high temperature. Although immersion tests can be performed using solutions of various materials in water, the practice is limited to testing only in water.

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

Note 1: Alternative practices for testing paint for water resistance include D1735, D2247 and D4585.

ASTM D 870-2020 Determination of Water Resistance of Coatings by Immersion Method

1.3 Values expressed in SI units shall be regarded as standards. The values given in parentheses are for reference only.

1.4 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.

1.5 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.