Ethyl silicate zinc-rich primers cure by the reaction of the vehicle with moisture, thereby providing a binder. As relative humidity and temperature vary during the day, so does the rate of cure. A certain minimum degree of cure is necessary prior to topcoating. It has been shown that the degree of cure of ethyl silicate zinc-rich primers can be measured by the chemical changes occurring using diffuse reflectance infrared spectroscopy. This solvent rub test has been shown to correlate well with the infrared spectroscopic results of some two-component ethyl silicate inorganic zinc systems.

The cure rating required for the application of specific topcoats must be agreed upon before the practice is used.

1.1 This practice describes a solvent rub technique for assessing the MEK resistance of ethyl silicate (inorganic) zinc-rich primers. The MEK resistance of some two-component ethyl silicate zinc-rich primers has been shown to correlate well with the cure of the primer as determined by diffuse reflectance infrared spectroscopy. The technique can be used in the laboratory, field, or in the fabricating shop. Practice D5402 is the preferred method for organic coatings.

1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.3 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. Specific hazard statements are given in Section 6. Consult supplier's Material Safety Data Sheet(s) for specific hazard information relating to the solvent used.