A two-part silicone sealant designed for use as a secondary sealant in a dual-sealed insulating glass unit, as well as in an insulating glass unit that will be structurally glazed. The product cures to a durable, high-modulus, flexible silicone seal that is chemically stable and creates a weathertight bond. It has excellent unprimed adhesion to glass and metal substrates, such as galvanized steel and aluminum.