Metallic black, 1-part, thixotropic, room temperature vulcanizing oxime silicone paste sealant.LOCTITE® SI 598 is a metallic black, 1-part, thixotropic, room temperature vulcanizing oxime silicone paste sealant. It cures on exposure to moisture in the air to form a tough, flexible, silicone rubber gasket. It resists ageing, weathering and thermal cycling without hardening, shrinking or cracking. This product is typically used in applications with an operating range of -54 to 260°C.