Si 2-Part Epoxy Primer is a water-based primer used to promote adhesion and prevent asphalt staining with our Mule-Hide 100% Silicone Roof Coating. Also used over areas of rusted metal to encapsulate rust. Mule-Hide Si 2-Part Epoxy Primer is not intended for exposure to the elements and must be top coated with Mule-Hide 100% Silicone Roof Coating within five days of application. Do not allow Si 2-Part Epoxy Primer to freeze.