Royston R28 Rubberized Mastic is a thixotropic, brush or spray applied asphalt coating for below grade applications. R28 is a time proven coating technology for providing corrosion protection to metal fittings, flanges, valves, tanks, mechanical couplings, anode connections and other difficult and irregular configurations.
R28 easy to apply by brush or rubber glove and can also be sprayed. Due to its thixotropic nature it resists drips and sags during application, but will become more flowable the more it is mixed. The R28 can also be sprayed via air or airless sprayers. The R28 may need to be thinned for spray applications below 60°F. R28 is available with its standard formulation or as a Zero VOC Mastic. The Zero VOC version uses a VOC exempt solvent to obtain its 0 g/L VOC rating.
Apply in two or three coats that each have a WFT of 20 mils. Allow the first coat to dry to the touch before application of the second coat, about 30 minutes. Never apply more than 40 mils in a single coat to prevent mud cracking. R28 is usually sufficiently dry after 1 1/2 hours for light handling and backfilling. Low temperature or high humidity conditions will lengthen the dry time.