4.1 Coatings that chemically change during the curing process, such as epoxies, vinyl esters, polyesters, alkyds and urethanes, become more resistant to solvents as they cure. These coatings should reach specific levels of solvent resistance prior to being topcoated and prior to placing in service; the levels of solvent resistance necessary vary with the type of coating and the intended service. Rubbing with a cloth saturated with the appropriate solvent is one way to determine when a specific level of solvent resistance is reached. However, the level of solvent resistance by itself does not indicate full cure and some coatings become solvent resistant before they become sufficiently cured for service.

4.2 The time required to reach a specific level of solvent resistance can be influenced by temperature, film thickness, air movement and, for water-borne or water-reactive coatings, humidity.

4.3 The test solvent’s effect upon the coating varies with coating type and solvent used. The coating manufacturer may specify the solvent, the number of double rubs, and the specific test results needed.

1.1 This practice describes a solvent rub technique for assessing the solvent resistance of an organic coating that chemically changes during the curing process. This technique can be used in the laboratory, in the field, or in the fabricating shop. Test Method D4752 is the preferred method for ethyl silicate zinc-rich primers.

1.2 This practice does not specify the solvent, number of double rubs, or expected test results.

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 the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Consult the supplier’s Material Safety Data Sheet for specific hazard information relating to the solvent used.